Abundance and distribution of a neustonic copepod in Magellan waters, Chile
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Abundance and spatial distribution of the neustonic copepodites of Microsetella
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rosea (Harpacticoida: Ectinosomatidae) along the western coast of Magellan, Chile
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ABSTRACT. The pelagic harpacticoid copepods Microstella rosea inhabits the sub Antarctic coast of
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South America, where its population biology and role in the southern plankton of Chile are unknown.
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During the oceanographic campaign CIMAR 16 Fjords (October 11 to November 19, 2010; 52º50’S to
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55º00’S; western Magellan region, Chile), 26 positives neustonic samples were collected (depth: 0-30
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cm), allowing to analyze the abundance and spatial distribution of copepodites and their environmental
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requirements. M. rosea copepodites (total length: 700-1,000 µm), the most abundant of holoplanktonic
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taxa within of the neustonic community (30% of the total abundance; 238,673 individuals), was
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represented at 100% of collection sites and was 0.5 times more abundant than calanoid copepods. They
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inhabit waters with temperatures between 6.5o and 8.5oC, with maximum abundance (1,000-10,000
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individuals/5 minute horizontal drag) only detected between 7.0 and 8.0oC (mean = 7.2 ± 0.7ºC).
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Additionally, M. rosea copepodites were detected in diluted waters with 26 to 33 psu (mean =29.8 ±
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4.1), with maximum abundance detected in waters between 29 and 31 psu. Almirantazgo Sound and
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Inutil Bay accounted for 65% of the total abundance of M. rosea, while the lowest values were detected
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in Beagle Channel (<4%). All area inhabited corresponds to an oxygenated estuary (Oximax
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conditions; mean 7.6 ± 2.4 mL O2 L-1). Given the abundance of M. rosea and its recurrence in the
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Magellan neuston, we will suggest to investigate the ecological functions of this copepod in other
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estuarine pelagic environments of southern Chile, which based on the present evidence are classified as
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stenothermal/stenohaline.
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Keywords: Copepoda, neuston, sub Antarctic zooplankton, estuaries, Oximax zone.
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Abundancia y distribución espacial de copepoditos neustónicos de Microsetella rosea
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(Harpacticoida: Ectinosomatidae) en la costa occidental de Magallanes, Chile (Crucero
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CIMAR 16 Fiordos)
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RESUMEN. El copépodo harpacticoídeo pelágico Microsetella rosea habita en el neuston subantártico
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de Sud América, desconociéndose tanto su biología poblacional como el rol en las comunidades
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planctónicas australes. Durante el crucero CIMAR 16 Fiordos (11 octubre al 19 noviembre, 2010;
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Abundance and distribution of a neustonic copepod in Magellan waters, Chile
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52º50’S a 55º00’S; zona occidental Magallanes, Chile), se colectaron 26 muestras neustónicas efectivas
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(0-30 cm profundidad), permitiendo analizar la distribución espacial y abundancia de los copepoditos
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de esta especie, así como sus requerimientos ambientales. M. rosea (700 a 1.000 µm longitud total) fue
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el componente holoplanctónico más abundante del neuston (30% de la abundancia total; 238.673
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individuos), estando representado en 48,4% de las estaciones y siendo 0,5 veces más abundante
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respecto de copépodos pelágicos calanoídeos. Los copepoditos se distribuyeron en aguas con
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temperaturas entre 6,0 y 8,5ºC, pero las abundancias máximas (1.000 a 10.000 ind./ 5 minutos arrastre
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horizontal) se detectaron entre 7,0 y 8,0ºC (media = 7,2 ± 0,7ºC). Los copepoditos se detectaron en
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estaciones con salinidades entre 26 y 33 ups (media =29,8 ± 4,1 ups), con las mayores abundancias en
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salinidades entre 29 y 31 ups. El Seno Almirantazgo y Bahía Inútil acumulan el 65% de la abundancia
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total de copepoditos de M. rosea, mientras que los valores menores se detectaron en el canal Beagle
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(<4%). La zona habitada por M. rosea representa un estuario oxigenado (zona Oximax; media = 7,6 ±
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2,4 mL O2 L-1). La abundancia y recurrencia de M. rosea en el neuston magallánico, sugiere investigar
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nuevas funciones ecológicas en otros ambientes pelágicos estuarinos de la zona austral de Chile y
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puede ser clasificada como una especie estenotérmica/estenohalina.
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Palabras clave: Copepoda, Neuston, zooplancton sub Antárctico, estuarios, zonas Oximax.
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INTRODUCTION
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Harpacticoid copepods are primarily benthic. A small proportion (< 0.5%) of harpacticoid species only
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inhabits the pelagic realm during all life (Boxshall, 1979; Uye et al., 2002). These pelagic harpacticoids
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have relatively active swimming ability, unique structural features such as an elongated worm-like
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body and either caudal setae that delay or slow their sinking velocity (Microsetella spp & Macrosetella
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spp) or a close association with floating substrates (e.g. the colonial cyanobacterium Trichodesmium;
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Calef & Grice, 1966; Tokioka & Bieri, 1966; O’Neil, 1998). Additionally, it has been reported that a
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member of the genus Microsetella live on aggregated and suspended organic matter (Alldredge, 1972;
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Ohtsuka et al., 1993; Green & Dagg, 1997; Uye et al., 2002; Zaitsev, 2005).
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Microsetella rosea is widely distributed in the sub Antarctic waters from southern end of South
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America (5 to 10°C) to western Antarctic waters, as well as in the subtropical warm waters of the South
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China Sea, the Mediterranean Sea and the Black Sea (http://copepodes.obs-banyuls.fr). Adult females
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Abundance and distribution of a neustonic copepod in Magellan waters, Chile
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can reach a weight of 0.02 mg and a maximum length of <800 µm. Members of this genus are
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numerically dominant and attain high levels of abundance in marine neustonic communities, especially
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in coastal waters (Anraku, 1975; Dugas & Koslow, 1984; Uye et al., 2002; Zaitsev, 2005).
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Compared to the vast information available on population dynamics and production of marine
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planktonic calanoids, few studies focus on marine and estuarine planktonic non-calanoids, particularly
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on the genus Microsetella (Paffenhöffer, 1993; Sabatini & Kiørboe, 1994; Uye & Sano, 1995; Uye et
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al., 2002). Uye et al. (2002) studied the population dynamics and production of M. norvegica in the
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inland Sea of Japan and found that reproductive activity occurs in the early fall and that brooding sacs
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reached a maximum of 16 eggs/sac. Under laboratory conditions, growth rates are dependent on water
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temperature (32 and 14 days at a temperature of 20 and 27°C, respectively) have been observed. These
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pelagic harpacticoid attain high population abundance (7x104 ind. m-3) with a maximum production
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rate of 4.9 mg C m-3 day-1 in October. During the winter, nauplii and copepodites disappear in
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December and the overwintering population is dominantly composed of adults, primarily large females.
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Hardy (2005) emphasizes that biodiversity levels and densities of neustonic organisms and how
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they vary spatially and temporally remain unknown as well as their role in sustain biogeochemical
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cycling and atmosphere-ocean exchange processes and as source of nutritional requirements for
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important trophic web in significant areas of the oceans. Given the lack of knowledge on the neustonic
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communities along the Chilean coast (Palma & Kaiser, 1993), the present research was originally
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proposed to describe the community structure and biodiversity of neuston in southern Chile.
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The reason for focusing research efforts on this section of the water column are: i) the neuston
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represents the boundary region of the air/water interface, and which can be thought of as the ocean’s
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skin, given that it is only a few centimeters (Hardy, 1991; Upstill-Goddard et al., 2003), thick and
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covers 71% of the planet’s surface, making it the largest ecosystem in the world; and ii) in order to
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understand how the neuston is influenced by environmental and oceanographic factors, such as
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temperature, solar radiation, marine pollution, salinity and density variations, effects of UV radiation,
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acidification and increasing temperatures in the oceans, etc. (Hardy, 1991; Rodríguez et al., 2000;
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Zaitzev, 2005), topics which are mentioned as an important theme of the oceanographic research
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associated to climate warming and oceanographic change in aquatic ecosystems of sub polar latitude
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(Zaitsev, 2005), and iii) ) the importance of the neustonic mesozooplankton as a crucial factor for
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feeding and survival of important resources such as the salmonid fishes in the northern California
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Current System (Brodeur, 1989; Pool et al., 2012).
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Abundance and distribution of a neustonic copepod in Magellan waters, Chile
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Similarly, latitudinal differences in the environmental functions provided by the neuston,
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namely fragmentation and transport of organic matter to greater depths, are not understood (Zaitsev,
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2005; Koski et al., 2007). In temperate zones, the neuston plays an important trophic role as a food
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source for meso- and macro-zooplankton and is a key component in the production of “marine snow”
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and the vertical transport of organic material from the surface of the oceans to greater depths (Conte et
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al., 1998; Hays et al., 2005; Zaitsev, 2005; Koski et al., 2007). In addition, the neuston zone represents
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the atmospheric-oceanic interface and therefore its importance stems from the fact that at small spatial
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scales (cm), physical processes critical to global conservation of biogeochemical cycles may occur (e.g.
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the exchange and balance of gases between both reservoirs).
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Members of genus Microsetella typically inhabit in the neuston layer. The importance of this
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section of the water column in their early life cycle as well as in the larval stages of commercially
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valuable species or species with ecological interest in Chile (e.g. the snail Concholepas concholepas;
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Di Salvo, 1988; Molinet et al., 2006; the snail Argobuccinum pustulosum, Gallardo et al., 2012; and the
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snail Fusitriton magellanicus, Cañete et al., 2012), its role in larval dispersion (Scheltema, 1986;
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Gallardo et al., 2012; Cañete et al., 2012), its utility in long term studies analyzing the influence of
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pollution on the neuston, as well as its role in sustain trophic requirements of numerous coastal filter-
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feeding pelagic and benthic species are unknown. In the latter case, it is relevant that in southern Chile
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there exists a significant amount of fresh water that could potential stratify the water column, producing
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vertical patterns of neuston, with the organic matter being capable of sustaining pelagic and benthic
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filter-feeders consumption (e.g. the family Mytilidae can accumulate between 15 to 25 kg m-2 in rocky
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shores of the southern Chile (Osorio, 2002; Hardy, 2005; Aldea, 2012; Cañete et al., 2014).
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In the waters of the Magellan Strait, typical pelagic calanoid and cyclopoid copepods have been
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previously studied (Marín & Antezana, 1985; Mazzocchi et al., 1995; Hamamé & Antezana, 1999;
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Marín & Delgado, 2001), with scarce reference to the pelagic harpacticoid such as of the genus
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Microsetella (Aguirre et al., 2012). However, work on pelagic harpacticoids copepods has not been
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widely cited in both sides of South American coast (Palma & Kaiser, 1993; Boltovskoy, 1999).
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Intensive seasonal study carried out in the Beagle Channel off Ushuaia, Argentina, made no mention to
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the presence of M. rosea in this location (Biancalana et al., 2007; Aguirre et al., 2012).
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The present research was designed in order to: i) record the abundance and spatial distribution
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of neustonic copepodites of M. rosea along of the west margin of the Magellan Region, Chile; ii)
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connect these ecological patterns with oceanographic parameters, in order to define whether this
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Abundance and distribution of a neustonic copepod in Magellan waters, Chile
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species is adapted to euryhaline or stenohaline conditions such as other members of the genus, and iii)
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to establish a comparison between Microsetella abundance and that of other holoplanktonic taxa
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collected during the CIMAR 16 Fjord campaign (spring, 2010).
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MATERIALS AND METHODS
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The sampling was conducted during the CIMAR 16 Fjords campaign (October 11 to November 19,
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2010). Areas covered include the western mouth of the Magellan Strait, (stations 7-15) up until the
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Beagle Channel (Navarino Island: stations 37-43). In the areas close to Dawson Island, samples were
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primarily collected in the Almirantazgo Sound and Inútil Bay (stations 51-60). Additionally, the west
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area of the channels and islands located towards the Pacific Ocean were included in the sampling area
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(stations 27-35) (Fig. 1). The RV Abate Molina platform was used for sampling. Originally, was
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planned a sampling along the eastern margin of the Magellan Strait; however, this was not possible due
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to difficulties in weather conditions (stations 1-6; not showed in Fig. 1).
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At each station, surface sampling was conducted with a neuston net (80 cm wide and 30 cm
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deep) with a 50 µm wide zooplankton mesh; this mesh net size was selected because has been applied
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in other studies in small copepods studies (Kršinić, 1998). This neustonic net consists of 4 lateral floats
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constructed of 3” diameter tubing and weighs approximately 20 kg. This type of net has been used
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previously to collect neustonic larvae of the marine gastropod Concholepas concholepas in northern
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Chile (Di Salvo, 1988). The net was (trawling) dragged along the surface (30-50 cm from the surface)
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for 8 minutes at stations 7, 8 and 9. However, given the high concentration of plankton collected, the
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drag time was reduced to 5 min at all subsequent sampling sites. According to Hardy (2005) layer’s
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classification system, the layer covered during the present study could correspond to centilayer and
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surface layer (1 to 100 cm depth). The speed of the boat was reduced to 1-2 knots. Only one haul was
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conducted per station. Samples were fixed with 5% neutralized formalin. Biomass and abundance data
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was standardized to the number of individuals or g per 5-minute drag due to a lack of flow-meter.
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At each station, the drag was performed with a rosette equipped with a CTD Sea Bird that was
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submerged to different depths according to the bathymetric features of each site (Data Report CIMAR
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Fjords 16). Since the neuston lives in the surface layers, data on temperature, salinity and dissolved
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oxygen content was averaged between 1 and 2 m of depth at each station.
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Abundance and distribution of a neustonic copepod in Magellan waters, Chile
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In the laboratory, total sample was sieved in a 30 µm mesh size net for wet biomass
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determination, including phytoneuston and zooneuston together. Following the size ranges
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classification of neustonic organisms proposed by Hardy (2005), in the present research we cover
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mainly micro- to mesoneuston (20 µm a 20 mm size). Samples were divided with a Folsom fractioning
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to 1/8th of total content to facilitate counting of neustonic holoplankton and Microsetella copepodites.
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Neuston taxa were identified by phylum, class and order, and were independently counted under a
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stereo- microscope.
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The copepod stages of Microsetella were identified following to Uye et al. (2002) and
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accounted for all individuals present in each sample. In the present study, only abundance data based
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on identification of copepodites was considered while other stages of the life cycle of M. rosea were
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not included (nauplius and adults). Some females with egg-sac were observed. Others components of
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the zooplankton were identified based on Palma & Kaiser (1993) and Boltovskoy (1999).
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According to Davies & Slotwinski (2012) some criteria for identifying M. rosea and for
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differentiating it from M. norvegica are: i) size, if over 0.8 mm it is likely M. rosea; ii) length of caudal
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rami setae, if nearly twice as long as the body then it is M. rosea, if shorter than it could be either
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species (setae could be broken); iii) M. rosea has spinules on the metasome and urosome, M. norvegica
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has spinules on the urosome; iv) M. norvegica caudal rami are slightly more divergent than M. rosea;
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and v) M. rosea may be pink in color. Both species has cited to Chilean coast (Pacheco et al., 2013).
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Samples were stored at the Laboratorio de Oceanografía Biológica Austral (LOBA),
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Department of Sciences & Natural Resources, Faculty of Sciences, Universidad de Magallanes, Punta
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Arenas, Chile.
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One-way ANOVA was used to compare the spatial distribution of Microsetella abundance and
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their relationship with oceanographic parameters in the study area. Prior to the analysis, data were
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normalized by logarithmic transformations log (x + 1) to meet the assumptions of normality and
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homogeneity of variances and show graphs with log scale. Pearson correlations were used to study the
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relationships between the environmental parameters and Microsetella abundance. If significant
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differences were found, areas were compared using the Tukey_Kramer test. Statistical analyze were
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performed using Sokal & Rohlf (1994).
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Abundance and distribution of a neustonic copepod in Magellan waters, Chile
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RESULTS
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Oceanography
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The spatial variability of three oceanographic factors (temperature, salinity and dissolved oxygen) were
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measured in the surface layers in stations analyzed during research expedition (Table 1). Only surface
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values were used, as the depth of neuston samples did not exceed 30 cm below the air/water interface
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(Liss & Duce, 2005).
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Water temperature superficial fluctuated between (6.163°C) 5 and (8.422°C) 8oC, with an
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average water temperature of 7.2XXoC in all area (SD, standard deviation = 0.59). The highest water
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temperatures were detected in Whiteside Channel and in Inútil Bay, while the lowest temperatures were
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detected along the eastern side of the Magellan Strait and in the interior of Almirantazgo Sound, near
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the glaciers discharge of the Darwin Ice Field (Table 1).
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Of the three oceanographic variables measured, salinity varied widely, ranging from 26 to 33
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psu, with an average value of 30.7 (SD = 0.92) (Table 1). Based on the classification criteria for
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estuarine conditions of southern Chile proposed by Valdenegro & Silva (2003), all samples in the study
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area were taken in Estuarine Waters (EW; 1-32) or in Modified Subantarctic Water (ASAAM; 32-33).
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Dissolved oxygen content ranged from 6.5-8.8 mL O2 L-1 seawater, with an average value of 7.4
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mL O2 L-1 (SD = 0.35 mL O2 L-1). The surface water column was oxygenated throughout the study
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area, with a maximum value in the interior part of Almirantazgo Sound, which is close to a glaciated
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area. According to Cañete et al. (2012b) the entire area surveyed would be classified as Oximax (values
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> 4 mL O2 L-1) (Table 1).
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Neustonic biomass/abundanceThe neustonic biomass collected fluctuated by up to two orders of
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magnitude, ranging from 0.1-30.5 g 5min-1 of horizontal drag (Mhd) (Fig. 2). The neustonic biomass
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was highest in protected areas such as Almirantazgo Sound/Inútil Bay (average = 13.3 g 5Mhd-1) and
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along the west arm of the Magellan Strait (between Capitán Aracena island and the west mouth of
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Magellan Strait) (average = 11.1 g 5Mhd-1), and lowest along the Beagle Channel (5.5 g Mhd-1). In all
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study area, the average biomass of neuston was 8.6 g/station (SD = 7 g/station), showing a dispersion
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coefficient of 77% (Fig. 2).
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The spatial pattern of the neustonic abundance followed a trend similar to the biomass, with
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maximum values in the Almirantazgo/Inutil Bay area (average = 18,350 ind 5Mhd-1 and lowest
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abundance in the Beagle Channel (average = 3,358 ind 5Mhd-1). The average abundance of the stations
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Abundance and distribution of a neustonic copepod in Magellan waters, Chile
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located between west side of the Dawson Island and the Pacific Ocean and along the occidental arm of
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the Magellan Strait varied between 7,172 and 7,337 ind 5Mhd-1 (Tabla 2). In all study area, the average
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abundance of neuston was 9,180 ind/station (SD = 10,281), indicative of a patchy distribution with a
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dispersion coefficient of 112% (Fig. 2).
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Abundance of the copepod Microsetella rosea
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The copepodites of Microsetella rosea were collected in all study area (Fig. 3). However, there are
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evident differences between zones, indicating wide spatial variability within west Magellan Region.
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For example, in the Almirantazgo Sound/Inutil Bay area (mid Magellan strait) it was recorded the
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maximum abundance of M. rosea, while the lowest abundance was recorded in stations along Beagle
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Channel and in open areas around Navarino Island with only 362 individuals by sample (ind 5Mhd-
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1
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individuals) (Table 3). Almirantazgo Sound and Inutil Bay accounted for 61.5% of the total abundance
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of M. rosea, while the lowest values were detected in Beagle Channel (<4%). The west arm of the
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Magellan Strait accounted near to 25% and the zone western to the Dawson Island to the 10% of the
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total abundance of copepodites of M. rosea .
)(Table 2). In total, copepodites accounted for 30% of the total abundance of neustonic taxa (238,673
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Stenohalinity or euryhalinity in Microsetella rosea?
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Copepodites of M. rosea inhabit surface waters with temperatures ranging between 6.5-8.5oC, with
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maximum abundance (1,000 to 10,000 ind 5Mhd-1) only detected in waters between 7.0-8.0oC (mean =
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7.2 ± 0.7ºC). However, an analysis of correlation between sea surface temperature and abundance of
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copepodites of M. rosea did not produce a significant relationship.
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Additionally, copepodites were found at stations with salinity levels between 26 and 33 psu
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(mean = 29.8 ± 4.1), with the highest abundance found in waters with salinity levels between 29 and 31
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psu. The area inhabited by M. rosea is classified as an oxygenated estuary (mean = 7.6 ± 2.4 ml O2 L-1)
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(Figs. 4a y b; Table 1). Overall, given the limited range of variation in these three oceanographic
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variables at the stations where the copepod M. rosea was found, it can be concluded that this pelagic
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harpacticoid copepod has a narrow range of physiological resistance to temperature and salinity in the
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west Magellan waters. However, an analysis of correlation between salinity (S) and abundance of
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copepodites of M. rosea (A) show a negative trend between both parameters, but not produced a
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Abundance and distribution of a neustonic copepod in Magellan waters, Chile
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significant relationship (best values of determination coefficient was obtained with a potential function
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of regression; R2 = 0.15; P> 0.05; N = 26; A = 8,103 + 26*S-16).
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Contribution of M. rosea in comparison to the rest of the neuston
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During the CIMAR 16 Fjords cruise, 238,673 individuals were counted from the neustonic
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meroplankton and holoplankton taxa (41.27% and 50.98%, respectively) (Table 3). Within the
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holoneustonic taxa, calanoid and harpacticoid copepods were the most abundant, including M. rosea in
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the last taxon. The abundance of copepodites of M. rosea was near twice superior respect to calanoid
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copepods (Table 3). An important fraction of juvenile of appendicularian was collected (4.3%).
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Within meroneustonic taxa, the numerically dominant group included the mytilid larvae
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(21.12%), followed of the unidentified larvae of a polychaete of the family Polygordiidae (16.5%) and
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cyphonaute larvae (2.41%). Cypris of barnacle (0.61%) and pluteus of echinoderms also were detected
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(Table 3). Decapod crustacean larvae were scarce (<0.26%). A total of seven holo- and nine
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meroneustonic taxa could be used as biotracer in the west Magellan region (Table 3).
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Thus, holoplanktonic component of the neustonic communities numerically dominate on the
meroplanktonic taxa during spring oceanographic condition in the west margin of Magellan region.
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DISCUSSION
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264
The present research was designed with the aim of i) to obtain a record of the abundance and spatial
265
distribution of neustonic copepodites of M. rosea along the west Magellan Region, Chile; ii) to connect
266
these ecological patterns with oceanographic parameters, in order to define if this species is stenohaline
267
or euryhaline as other members of the genus, and iii) to establish a comparison between Microsetella
268
abundance and that of others holoplanktonic taxa collected onboard of the CIMAR 16 Fjord campaign
269
(spring, 2010). It was important, also, in practical terms, to select some neustonic components that
270
could be used as biotracer of physical process associated to transport, dispersal, connectivity or
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aggregation of the Magellan plankton.
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Abundance and spatial distribution of M. rosea in Magellan waters
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M. rosea is a pelagic, neustonic, harpacticoid copepod that inhabits the interior waters of Magellan
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channels, at southern Chile (Razouls et al., 2005-2014). In the present study, it was shown that this
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Abundance and distribution of a neustonic copepod in Magellan waters, Chile
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species inhabits surface waters within specific areas of the western margin of the Magellan Region,
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Chile, where it can become the most numerically dominant species of copepods as well as the most
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dominant taxa in the neuston. M. rosea is distributed in all study area (Fig. 3, Table 3).
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The Magellan neuston was composed of holoplanktonic and meroplanktonic stages. Shanks &
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Carmen (1997) indicate that larvae of polychaetes are strongly associated with marine snow while that
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Shanks & Walters (1997) cited the massive presence of holoplankton, meroplankton, and meiofauna
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associated with marine snow. In the present study, furthermore of the high abundance of Microsetella
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and bivalves larvae, polychaete larvae were too abundant (Table 3). The most abundant and frequent
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polychaete larvae was named as “Banana larvae”, which recently has been identified as a potential
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Polygordiid larvae (Dra P. Ramey-Balci, com.pers.; Ramey-Balci & Ambler, 2014) and between
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crustacean larvae dominates those of that Munida subrugosa, although in low number in reference to
287
findings of León et al. (2008) An important fraction of larvae of echinoderms and cyphonautes larvae
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of bryozoans were detected being relatively recurrent in these neustonic samples (Table 3).
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The population density of M. rosea in the neuston in inner channels within the western sector of
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the Magellan Region (103-104 ind 5Mhd-1) is approximately one times greater than that of calanoid
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pelagic copepods detected in this same project (Table 3). Similar magnitudes of abundance were
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detected for the species M. norvegica in the inland of Japan Sea (Uye et al., 2002), where too the
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biomass can reach close to 100 mg C m-3 in the fall. Inversely, in the Adriatic Sea copepodites and
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adults of Microsetella spp showed minor presence respect to calanoids, Cyclopoida, oncaeids and
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oithonids copepods (Kršinić & Grbeco, 2012).
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One aspect not considered in the present study is the vertical distribution of the M. rosea
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copepodites. The neustonic sampling only considered the vertical distribution in the first 30 cm of this
298
layer. However, a widest vertical sampling could to demonstrate if this species is distributed to deepest
299
layers of the water column. Finally, it is worth nothing that despite a long tradition of zooplankton
300
studies in the Magellan Region, a review of the taxonomic and ecologic works of Mazzocchi et al.
301
(1995), Antezana (1999) and Marín & Delgado (2001) revealed there is no reference to the presence of
302
M. rosea in copepod samples. However, Fernández-Severini & Hoffmeyer (2005) cited the presence of
303
diverse species of pelagic harpacticoid copepods around Beagle Channel during summer condition.
304
The absence of M. rosea copepodites in Magellan waters in previous studies could be due to
305
large aperture size of mesh net. In our study, we use a mesh net of 50 µm while that in other studies
306
have cited sizes over 200 µm (Mazzocchi et al., 1995; Antezana, 1999; Defren-Janson et al., 1999;
10
Abundance and distribution of a neustonic copepod in Magellan waters, Chile
307
Marín & Delgado, 2001; Biancalana et al., 2007 & 2012; Guglielmo et al., 2014). Alternatively, it is
308
possible that the copepodites live only in the surface layers of water column and the horizontal drag
309
could be a good mechanism to collect abundant specimens; sampling strategies of previous studies has
310
considered only the vertical tow of the zooplanktonic net, which could to produce a lowest abundance
311
of this copepod (Kršinić & Grbec, 2012).
312
The spatial distribution and the levels of variability detected in neustonic Microsetella
313
population in the west margin of Magellan region, offer an interesting field of research to analyze the
314
relationship between physical processes as a primary determinant of the dynamics of estuarine
315
ecosystems (Mann & Lazier, 1991), providing the environmental conditions and the physical structure
316
within which the biological processes occur. Thus, neustonic communities and populations of the study
317
area could to offer opportunities to study the meso-scale spatial variability (Garçón et al., 2001) on
318
important biological phenomena arising from the interaction among physical processes, physiology and
319
behavior of the estuarine neustonic organisms.
320
321
Stenohalinity/euryhalinity in Microsetella rosea?
322
The spatial distribution of the neustonic communities can be influenced by diverse environmental and
323
oceanographic factors, such as temperature, solar radiation, marine pollution, salinity and density
324
variations, effects of UV radiation, acidification and increasing temperatures in the oceans, etc.
325
(Zaitzev, 2005). For this reason to know their physiological requirements is important to explain the
326
spatial distribution of estuarine taxa. Copepodites of M. rosea inhabit surface waters with temperatures
327
ranging between 6.2-8.4oC, with maximum abundance (1,000 to 10,000 individuals 5Mhd-1) only
328
detected in waters between 6.0-7.5o C (mean = 7.2 ± 0.7ºC). These facts suggest two situations: i) low
329
variation of salinity in the western side of Magellan Region, and ii) a stenothermic behavior of M.
330
rosea copepodites.
331
However, is necessary to study this response in other ontogenetic stages of the life cycle of this
332
species respect to the surface temperature. León et al. (2008) showed that most larval stages of the
333
squat lobster Munida gregaria in the southern Chile were temperature-dependent, and that the salinity
334
range of the youngest zoea was wider than that of oldest larvae and post-larvae, coinciding with an
335
ontogenetic distributional change from estuary to oceanic stations on the shelf, similar to other pelagic
336
taxa as Siphonophora living in cold waters of southern Chile (Palma et al., 2014).
11
Abundance and distribution of a neustonic copepod in Magellan waters, Chile
337
Additionally, were found the copepodites in stations with salinity between 26 and 33 psu (mean
338
= 29.8 ± 4.1), with the highest abundance of M. rosea copepodites found in waters with salinity ranged
339
between 29 and 31 psu. Overall, given the limited range of variation in these three oceanographic
340
variables at the stations where the copepod M. rosea was found, it can be concluded that the pelagic
341
harpacticoid copepod has a narrow range of physiological resistance to change in temperature and
342
salinity and could be classified as stenothermic and stenohalinic, respectively. Additionally, the area
343
inhabited by M. rosea is classified as an oxygenated estuary (mean = 7.6 ± 2.4 mL O2 L-1) (Table 1;
344
Fig. 4a y 4b).
345
The spatial distribution of M. rosea in the western margin of the Magellan Region seems be
346
regulated by changes in salinity, such as other members of the genus Microsetella. Yamazi (1956)
347
found that M. norvergica inhabits areas near the mouths of bays rather than sites close to river mouths
348
or other freshwater inputs. Uye & Liang (1998) found that in the inland Japan Sea, M. norvegica has a
349
low population density in water with salinity levels <30 psu. Uye et al. (2002) indicate that M.
350
norvegica is a stenohaline species that does not tolerate large variations in salinity. M. rosea reaches
351
greater numbers in waters with salinity ranged between 29 and 31 psu in Magellan waters (Figure 6b).
352
Similar situation was found for M. norvegica in the Beagle Channel by Aguirre et al. (2012), detecting
353
presence around of the year with abundances between 0.1 and 66.0 ind m-3. The difference of
354
abundance of both species of Microsetella in the Beagle Channel could be due to that Aguirre et al.
355
(2012) developed their study near to M. pyrifera kelp bed, while that during CIMAR 16 Fjord the
356
sampling stations were located in the center of each channel or in open waters. Guglielmo et al. (2014)
357
describe the composition and abundance of holoplanktonic polychaetes in Magellan waters where only
358
some species seem be affected by salinity (spatial distribution and abundance of Pelagobia
359
longicirrata and Tomopteris planktonis were negatively related to chlorophyll-a and positively affected
360
by salinity).
361
The spatial distribution of M. rosea seem be not affected by dissolved oxygen in west Magellan
362
waters. This gas is unlimited in this area and Cañete et al. (2012) has incorporated the term Oximax to
363
made reference to oxygenated waters of southern cold temperate latitudes. To probe the response of M.
364
rosea copepodites to largest ranges of variation of the dissolved oxygen will need to sample other
365
Magellan basins with less ventilation or establish comparison with other coastal zones of Chile with
366
minimum zones of dissolved oxygen (OMZ) (Thiel et al., 2007; Pacheco et al., 2013).
367
12
Abundance and distribution of a neustonic copepod in Magellan waters, Chile
368
Microsetella abundance versus others holoplanktonic taxa in Magellan waters
369
There are scarce comparative studies on the mesozooplankton in estuarine Magellan waters. During the
370
Joint Chilean-German-Italian Magellan "Victor Hensen" campaign (November 1994), distributional
371
pattern was studied and community analyses of mesozooplankton were made at seven stations in the
372
Magellan region (Defren-Janson et al., 1999). They detect: i) a high number of individuals were
373
collected in the area Magdalena to Brecknock Channels, at stations with a mixed water column. In the
374
southern part (Beagle and Ballenero Channels), low zooplankton abundance were associated with a
375
stratified water column due to melt water from several glaciers. Contrary to our study, in the spring
376
1994 the holoplankton dominated the assemblages (83-97%), where the copepods were by far the most
377
abundant taxon, contributing to more than 2/3 of the total zooplankton numbers. They not made
378
reference to the presence of Microsetella in these samples.
379
Patch of abundance of small copepods could to be influenced by frontal zone (Zervoudaki et al.,
380
2007). In the west Magellan Region is common the presence of frontal zones detected by accumulation
381
of ice, detached macroalgae as Macrocystis pyrifera kelp, changes of color of surface waters and
382
accumulation of foam in the surface layer (Valle-Levinson et al., 2006). The high abundance (1,000-
383
10,000 ind 5Mhd-1) in some stations of the CIMAR 16 Fjords could be due to the presence of frontal
384
zones given the wide difference in orders of magnitude in the abundance of M. rosea copepodites
385
between stations (Fig. 4a y 4b). However, we need to analyze others meteorological and oceanographic
386
variables to explain the dynamic pattern of abundance and spatial distribution of the Magellan neuston.
387
Kršinić & Grbeco (2012) indicates that copepodites of the harpacticoids Microsetella norvegica
388
and M. rosea are particularly dominant in the euphotic zone of the Adriatic Sea (1 to 5 m depth). In this
389
study, pelagic harpacticoids represented an average of 4.4% of the total number of copepodites and
390
adult copepods from the surface to a depth of 50 m, and 6.7% between 50 and 100 m depths. High
391
harpacticoid abundance values were also recorded at only some stations showing a patchy spatial
392
pattern, with a maximum of 1,800 ind m-3 sampled at a depth of 20 m and dominated by Microsetella
393
norvegica and M. rosea. The highest average harpacticoid abundance (450 ind m-3) was recorded
394
during summer season, representing 24% of the total number of copepodites and adult copepods.
395
396
Microsetella rosea and the composition of Magellan marine snow
397
One of the adaptive strategies employed by pelagic harpacticoid copepods is their ability to attach and
398
hold onto particulate organic matter floating and dispersed in the water column, which acts as a means
13
Abundance and distribution of a neustonic copepod in Magellan waters, Chile
399
of transport, and in turn as a source of food available in the surface layers of the ocean (Fig. 3a). The
400
fragmentation of this material by Microsetella reduces its size/weight allowing its consumption by
401
other smaller microphages, and through the production of fecal pellets and the shedding of its shell, it
402
can make a significant carbon contribution to the surface as well as deeper zones (Lampitt, et al., 1993;
403
Uye et al., 2002; Kiørboe, 2000). Particularly, is important the formation and fate of marine snow due
404
to the change in the structure of organic matter produced in thin layers of water column, having large-
405
scale or global implications (Kiørboe, 2001).
406
These actively swimming copepods have two important adaptations that facilitate an association
407
with particulate organic matters floating in the neuston area: an elongated cylindrical body, long and
408
spiny caudal setae that delay their sinking velocity and help them stick to “marine snow” or macro
409
aggregates produced by colonial diatoms and cyanobacteria (O'Neil, 1998; Uye et al., 2002). All these
410
adaptations were possible to observe in the samples collected aboard the CIMAR 16 Fjords and suggest
411
the need for further research, in the short term, in order to understand the feeding behavior,
412
physiological adaptations and reproductive strategies of this species with live samples.
413
Likewise, in this research and in the microscopic observation of fragmented plant tissue present
414
in the neustonic samples collected aboard the CIMAR 16 Fjords, it was possible to detect residual
415
tissue possible derived from kelp forest, such as Macrocystis pyrifera, a common and abundant species
416
and landscape in the coastal area of the inner channels in the Magellan Region (Ríos et al., 2007).
417
Thus, it is necessary to characterize the chemical origin of neustonic organic particulate matter and its
418
role in planktonic feeding, including M. rosea and other pelagic organisms. Recently, Geange (2014)
419
reported large volumes of photosynthetic tissue derived from M. pyrifera kelp that may finally
420
constitute a significant portion of the organic particulate material in which the neustonic grazers
421
feeding could to be sustained. Previously, Lucas et al. (1981) identified the heterotrophic utilization of
422
mucilage released during fragmentation of two species of kelp (Ecklonia maxima and Laminaria
423
pallida). Conte et al. (1998) describe an episodic flux of organic matter derived from the neustonic
424
population of Sargassum spp in the tropical Atlantic Ocean producing a significant seasonal
425
enrichment of the deep sea bottoms.
426
Other types of organism that could aid in diversifying the sources of organic particulate matter
427
present in the neuston samples collected aboard the CIMAR 16 Fjords include microalgae, particularly
428
diatoms forming chains as well as some dinoflagellates. Cañete et al. (2013a) found that some
429
phytoneustonic samples had a biodiversity of 33 species of diatoms and 35 species of dinoflagellates,
14
Abundance and distribution of a neustonic copepod in Magellan waters, Chile
430
and one species of silicoflagellata. In total, 74 species were collected. However, many Magellan
431
phytoplankton cells show large size, suggesting than M. rosea could to sustain their feeding on micro-
432
or nanoplankton, debris, mucous or cells with <20 µm diameter due to their small size of mouth.
433
According to Alvés de Souza et al. (2008) some functional groups or guilds of the marine/estuarine
434
phytoplankton assemblages collected in the southern Chile is composed of about 131 species; 74% of
435
these species are diatoms, 19% dinoflagellates and 7% nanoflagellates. Thus, in reference to this paper,
436
the neustonic phytoplankton collected in the CIMAR 16 fjords formed chains, have large diversity of
437
shape cells with many spines and could be classified as R-strategist.
438
Other aspect that could to explain the actual spatial pattern of Microsetella copepodites is the
439
spatial distribution of chlorophyll-a, where is possible to detect four stages of production along the
440
western Magellan margin (Hamamé & Antezana, 1999) in relation to salinity, temperature and
441
stratification of water column. These stages are: i) in Paso Ancho- Magdalena Sound showed a shallow
442
chlorophyll maximum (ca. 5 mg m-3 at 0-20 m) in a vertically homogeneous cold and brackish water
443
column; ii) in the section Magdalena, Cockburn and Brecknock channels had relatively lower
444
chlorophyll concentrations (2-3 mg m-3 at 0-50 m), minor stratification of salinity and a surface lens of
445
warmer water with direct Pacific Ocean influence; iii) in the Ballenero Channel-Nord-western arm of
446
Magellan Strait had a subsurface layer of high chlorophyll concentration (>4 mg m -3) in a vertically
447
stratified water column of two salinity layers and three temperature layers; and, iv) in the Beagle
448
Channel presented a subsurface chlorophyll maximum (>4 mg m-3) extending to the bottom, and
449
vertically homogeneous salinity and temperature distribution.
450
However, some preliminary antecedents of nutrients availability around stations located
451
between Almirantazgo Sound and Inutil Bay during CIMAR 16 Fjords, indicate that the area with
452
higher abundance of Microsetella could be classified as oligotrophic considering the low values of
453
phosphate (<0.5 µM), nitrate (<2 µM) and silicates (<1 µM) (Vargas et al., 2011).
454
Members of genus Microsetella seem be omnivorous because their diet including abandoned
455
larvacean houses (Alldredge, 1972, 1975 & 2005; Vargas et al., 2002), “macroscopic aggregates of
456
marine snow” (Alldredge & Youngbluth, 1985), including diatoms debris (Alldredge & Gotschalk,
457
1988; Alldredge & Silver, 1988), conforming a pelagic fragmented habitat (Atmar & Patterson, 1993).
458
In the present study, we collect appendicularian specimens in only 13 stations in the west margin of the
459
Magellan Region (Table 4), but not evidence of trophic relationship between both taxa were observed.
460
15
Abundance and distribution of a neustonic copepod in Magellan waters, Chile
461
Other roles played by the neustonic layer in Magellan waters
462
Cañete et al. (2015, in litteris) in a small embayment of the Magellan Region, has also observed that
463
the neustonic zone may represent an important route for the dispersion of subantarctic meroplankton
464
and juveniles stages of bivalves. Recently, levels of 103 to 104 pelagic juveniles of the brooder clam,
465
Gaimardia trapesina, have been detected in the interior of Porvenir Bay. In the last case, it would be
466
possible to postulate that this bivalve, possess other dispersal strategies apart from the traditional
467
rafting on the M. pyrifera kelp (Edgard, 1987; Highsmith, 1985; Hellmuth et al., 1994; Thiel, 2003;
468
Thiel & Gutow, 2005). In the present study, the presence of large abundance of larvae of Polygordiid
469
polychaete, cyphonautes of bryozoans, echinoids and some decapods crustacean confirm this role
470
(Table 3).
471
Cañete et al. (2013b) point out that in the Magellan channels the adults of the benthic
472
polychaete Platynereis australis attain pelagic behavior during reproductive maturation allowing it to
473
also adopt diverse strategies of pelagic transport through their pelagic adult stages, in addition to
474
gametes and larval transport. Thus, they postulated that some benthic invertebrates of Magellan
475
estuaries could to display a diverse array of dispersal strategies using temporally the neustonic layer, in
476
response to the large island fragmentation landscape and the patch habitat of the kelp M. pyrifera.
477
Other typical example of pelagic schooling behavior is showed by the crustacean Munida subrugosa in
478
the channels from southern Chile, which shows swimming behavior of juveniles and adults specimens
479
(León et al., 2008).
480
Due to the presence of at least 26 taxa represented by their larvae in the western Magellan
481
neuston (Table 4), the larval transport through this layer could to have important biological
482
implications for direct effects of tides, winds, currents etc. on the aggregation and dispersal of this
483
mero- and holoneuston, producing biogeographic and biodiversity affinities between Atlantic and
484
Pacific coast of the Magellan Region (Gaines et al., 2007; Tilburg et al., 2012). The large number of
485
larval stages in the west Magellan neustonic samples is coincident with the spring spawning cycle and
486
phenological reproductive behavior of some Magellan gastropods, echinoderms and crustaceans
487
(Oyarzún et al., 1999; Fernández-Severini & Hoffmeyer , 2005; Aguirre et al., 2012; Cañete et al.,
488
2012a).
489
Future studies could to probe how the neustonic layer could to be able to sustain larval
490
connectivity between different benthic and planktonic populations in both sides of the Magellan region
491
(Pineda et al., 2007). The most frequently winds are one-directional and are affected by the influence
16
Abundance and distribution of a neustonic copepod in Magellan waters, Chile
492
of the West Wind Drift Currents directed to West to East along of the sub Antarctic Circle (Fell, 1962;
493
Leese et al., 2010). Molecular evidence of the addressing of the mutational changes in the Magellan
494
limpet Nacella magellanica (González-Wevar et al., 2012) and in a species of isopod (Leese et al.,
495
2010) suggest a West-East trend in the dispersal pattern around Magellan region and sub Antarctic
496
Circle, respectively.
497
Another aspect that should be investigated is the ability of M. rosea, and other members of this
498
genus, to preserve the normal behavior of harpacticoid copepods that inhabit the benthos. Recently,
499
Pacheco et al. (2013) detected two species of Microsetella in the subtidal soft bottom zones in northern
500
Chile emerging from the sediment into the water column defined as diel migration. Therefore, it is
501
possible that spatial variations in the copepod M. rosea abundance in the Magellan Region, may be due
502
to such behavior and that it may have been influenced by the time at which neustonic samples were
503
collected and the depth of the stations. However, all stations sampled during CIMAR 16 Fjords are
504
deeper than 32 m, attaining down to 1,120 m depth (Table 1). Thus, the origin of the neustonic
505
population of M. rosea in Magellan waters could be supplied by shallow coastal areas and horizontal
506
transport.
507
Others roles of the neustonic harpaticoids are as preys. Green & Dagg (1997) made reference to
508
the value of the mesozooplankton association with medium to large marine snow aggregates in the
509
northern Gulf of Mexico. Also, neustonic cyclopoids could to retard the vertical flux of zooplankton
510
faecal material through recycling (González & Smetacek, 1994).
511
In addition, we need to verify the importance of the neuston as a biological tracer of small-scale
512
biophysical processes in coastal marine waters as well as to study latitudinal variation in the southern
513
Chilean coast. In our study, not direct relationship between salinity and the M. rosea abundance was
514
observed (Table 2). This situation could be associated to that in the surface Magellan waters sampled
515
during CIMAR 16 Fjord there is minor oceanographic fluctuations in temperature and salinity. Cañete
516
et al. (2013b) demonstrate that in neustonic samples collected during CIMAR 18 Fjord (winter, 2012)
517
carried-out between Guafo Channel and Elephant Estuary, southern Chile, there is a positive and
518
significant lineal relationship between the salinity and abundance and biomass of neuston (range of
519
salinity between 5 and 33 psu). This fact could to incorporate to the neuston as an important
520
oceanographic monitoring tool to track the estuarine, diluted waters into inner channels off southern
521
Chile (Palma et al., 2014). Previously, Johan et al. (2012) have detected that the spatial distribution of
522
copepods follow the salinity gradient in the tropical estuary of Perai River, Malaysia.
17
Abundance and distribution of a neustonic copepod in Magellan waters, Chile
523
The actual spatial pattern of the estuarine neustonic communities from Magellan waters could
524
be modified if the ice melting and rainy conditions change in direct relationship to global warming in
525
the southern Chilean coast. Therefore, a permanent monitoring of subantarctic neustonic communities
526
could be highly recommended.
527
528
ACKNOWLEDGEMENTS
529
530
The authors would like to thank to the Servicio Hidrográfico y Oceanográfico de la Armada (SHOA,
531
Chile) and the financial support to this project (CONA C16F 10-014), as well as to RV Abate Molina
532
crew, Instituto de Fomento Pesquero, Chile (IFOP), for providing the facilities necessary to collect
533
neustonic samples during the CIMAR 16 Fjord cruise, We would also like to thank the Program GAIA
534
Antártica (MAG1203), Contract MINEDUC-UMAG, for supporting the translation of the original
535
manuscript. Special thanks to the Programs CIMAR 18 and CIMAR 20 for providing partial funds to
536
support this publication. Special thanks to Ms. Sc. Jaime Ojeda for collection of these neustonic
537
samples during CIMAR 16 Fjord campaign. We thank the identification of neustonic phytoplankton by
538
Ms. Sc. Cristian Garrido (IFOP, Chile).
539
540
541
542
Aguirre, G.E., F.L. Capitanio, G.A. Lovrich & G.B. Esnal. 2012. Seasonal variability of
543
metazooplankton in coastal sub-Antarctic waters (Beagle Channel). Mar. Biol. Res. 8: 341-
544
353.
545
546
547
548
549
550
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800
801
27
Abundance and distribution of a neustonic copepod in Magellan waters, Chile
802
Table 1. Surface oceanographic data (average between 1 and 2 m in depth) from CIMAR 16 Fjord
803
cruise (October-November 2010) at stations where neustonic samples were collected in the western
804
margin of the Magellan region, southern Chile.
STT
Latitude
Longitude
Date
7
8
9
10
11
13
14
15
27
30
35
36
37
38
39
40
41
42
43
52
53
54
55
56
57
60
53.9133
53.9035
53.7587
53.4048
53.1800
52.8252
52.6500
52.7328
54.1813
54.4028
54.7878
54.9288
54.8783
54.9033
54.9833
54.9072
54.9117
55.025
55.3722
54.3965
54.2150
53.9233
53.6085
53.5473
53.4650
53.5783
71.0933
71.5650
72.0043
72.8862
73.3467
74.1972
74.7833
74.9500
70.9263
71.0212
71.1248
70.7152
69.9383
69.4667
69.0333
68.4705
67.725
66.8083
66.6675
69.2242
69.8817
70.2600
70.2667
69.8563
69.4992
70.5883
31-Oct
31-Oct
31-Oct
31-Oct
30-Oct
30-Oct
30-Oct
30-Oct
04-Nov
04-Nov
05-Nov
05-Nov
05-Nov
06-Nov
06-Nov
06-Nov
07-Nov
07-Nov
07-Nov
22-Oct
23-Oct
23-Oct
02-Nov
02-Nov
02-Nov
01-Nov
Time
Depth
(m)
23:29
532
18:09
520
11:30
336
2:25
671
19:47
1120
8:25
505
4:48
65
2:17
91
16:59
349
20:17
246
12:25
411
18:32
81
23:00
374
2:50
283
7:42
32
23:22
159
4:38
166
10:24
95
20:00
91
21:07
250
2:00
246
7:35
479
16:57
266
20:37
40
23:25
42
5:27
100
Mean
Standard
Deviation
Temperature
(ºC)
7.224
7.276
7.235
6.869
6.806
7.129
7.927
8.106
7.637
7.175
7.061
7.261
7.277
7.855
6.696
6.543
7.475
7.179
7.096
6.163
6.198
6.259
7.693
8.422
8.126
6.794
7.2
Salinity
30.533
30.551
30.676
28.897
29.882
29.669
31.996
32.777
30.569
30.662
30.904
30.535
30.000
29.974
31.289
31.250
31.024
32.186
32.288
29.165
30.130
30.224
30.374
30.517
30.49
30.407
30.7
O2
(ml O2 L-1)
7.284
7.790
7.318
7.279
7.077
7.339
6.784
6.655
7.925
7.459
7.940
7.621
7.417
7.474
7.088
7.225
7.645
7.450
7.232
7.088
7.100
7.429
8.270
7.541
7.107
7.455
7.4
0.59
0.91
0.35
805
806
28
Abundance and distribution of a neustonic copepod in Magellan waters, Chile
807
Table 2. General summary of the total neustonic biomass and abundance as well as the total abundance
808
of the copepod Microsetella rosea collected in the CIMAR 16 Fjords campaign in 4 macrozones
809
located in the west margin of the Magellan Region, Chile (October-November 2010). Average values ±
810
standard deviation. Mhd = minutes of horizontal drag. No significant differences were detected
811
between macrozones (F3,25: 8.63; P > 0.05)
812
Macrozone
Almirantazgo Sound- Inútil Bay
(Magellan Strait) (7 stations) (salinity
= 29.6 ± 1.64)
West arm of the Magellan Strait
(8 stations)
(salinity = 30.6 ± 0.46)
West islands located between
Dawson Island – Pacific Ocean (4
stations) (salinity = 30.7 ± 0.17)
Southern Branch of the Beagle
Channel and Navarino Island (7
stations) (salinity = 31.1 ± 0.92)
Neuston biomass
(g 5Mhd-1)
Neuston
Abundance
(ind 5Mhd-1)
Microsetella rosea
Abundance
(Ind 5Mhd-1)
13.3 ± 9.4
18,350 ± 11,594
6,307 ± 5,993
11.1 ± 3.25
7,172 ± 3,888
2,225 ± 3,693
7.2 ± 1.83
7,337 ± 5,263
1,826 ± 2,009
3,358 ± 4,321
361 ± 263
1.5 ± 8.27
813
814
29
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
30
Table 3. Comparative analysis of neustonic zooplankton collected during the CIMAR 16 Fjords cruise
(Spring 2010) along the western margin of the Magellan Region, Chile. A = Total Abundance (%; N
total = 238.673 individuals). Larval type is referred to the number of different families or orders,
especially in polychaetes and crustaceans, respectively. Total percentage no give 100% because there
are some larval types not identified or were scarce.
TAXA
Holoneuston
Cnidaria
Ctenophora
Pelagic Polychaeta
Calanoid copepods
M. rosea copepodites
Appendicularia
Fishes eggs
Meroneuston (larvae)
Nemertea (Müller)
Polychaeta (11 types)
Sipunculida (pelagosphaera)
Barnacles (nauplius + cypris)
Decapod crustaceans
Bryozoa (cyphonaute)
Gastropoda (bilobed larvae)
Bivalvia (right charnel + umbonated)
Echinodermata (pluteus)
TOTAL
A (%)
Frequency (number of cases)
0.200
0.002
0.008
16.395
29.993
4.291
0.082
5
1
1
26
26
13
5
0.002
16.446
0.002
0.606
0.258
2.410
0.007
21.118
0.419
92.243%
1
24
1
11
11
19
2
18
11
30
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
31
Figure 1. Map of the CIMAR 16 Fjord campaign with the distribution of the stations where neustonic
samples were obtained for analysis of abundance and spatial distribution of the pelagic harpacticoid
Microsetella rosea in the west Magellan Region, Chile (October-November, 2010).
31
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
32
100000
10000
1000
100
10
1
7 8 9 10 11 13 14 15 27 30 35 36 37 38 39 40 41 42 43 51 52 54 55 56 57 60
Neustonic biomass
Stations
Neustonic abundance
Figure 2. Neustonic biomass (g 5Mhd-1) and abundance (ind 5Mhd-1) collected during CIMAR 16
Fjords cruise (October-November, 2010) in the western margin of the Magellan Region (both
expressed in log scale; include phytoneuston and zooneuston together).
32
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
33
Figure 3. Spatial distribution of copepodites of the pelagic harpacticoid copepod Microsetella rosea in
the west Magellan region, southern Chile (Spring, 2010). Abundance expressed as ind 5Mhd-1.
33
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
Total abundance Microsetella
(log)
34
100000
N = 26
10000
1000
100
10
1
5
6
7
8
9
Sea surface temperature (ºC)
10
100000
Total abundance Microsetella
(log)
N = 26
10000
1000
100
10
1
25
27
29
31
Sea surface salinity
33
Figure 4. Temperature ranges and average salinity of the surface layers of the water column (1 to 2 m)
analyzed during the CIMAR 16 Fjords cruise in the spring of 2010 to determine the oceanographic
requirements of Microsetella rosea copepodites. Abundance expressed as ind 5Mhd-1.
34