Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
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Version Final 18-8-2015
Abundance and spatial distribution of the neustonic copepodites of
Microsetella rosea (Harpacticoida: Ectinosomatidae) along the western
coast of Magellan, Chile
Juan I. Cañete1, Carlos S. Gallardo2, Carlos Olave3, María S. Romero4,
Tania Figueroa1 & Daniela Haro5
1
Lab. Oceanografía Biológica Austral (LOBA), Facultad Ciencias, Universidad de
Magallanes Punta Arenas, Chile
2
Instituto Ciencias Marinas y Limnológicas, Facultad de Ciencias
Universidad Austral de Chile, Valdivia, Chile
3
4
Centro Regional de Estudios, CEQUA, Punta Arenas, Chile
Dpto. Biología Marina, Facultad Ciencias del Mar, Universidad Católica del
Norte, Coquimbo, Chile
5
Lab. Ecol. Molecular, Facultad Ciencias, Universidad de Chile, Santiago, Chile
Corresponding author: Juan I. Cañete ([email protected])
ABSTRACT. The pelagic harpacticoid copepods Microsetella rosea inhabits the cold,
temperate coast of South America, where its population biology and ecological role in the
southern Chile neuston is unknown. During the oceanographic campaign CIMAR 16
Fjords (October 11/November 19, 2010; 52º50’S to 55º00’S; western Magellan Region),
26 neustonic samples were collected (depth: 0-30 cm), to analyze the abundance, spatial
distribution of copepodites and their oceanographic requirements (temperature, salinity
and dissolved oxygen; 0-1 m depth). M. rosea copepodites (total length: 700-1,000 µm),
the most abundant holoneustonic taxa (30% of total abundance), was present in all
stations and was 0.5 times more abundant than calanoids. Copepodites inhabit waters
with temperatures ranged between 6.5-8.5oC, with maximum abundance (1,000-10,000
individuals/5 minute horizontal drag) when mean temperature was 7.2 ± 0.7ºC.
Copepodites were detected in waters with 26-33 psu (mean =29.8 ± 4.1), with maximum
abundance between 29-31 psu. Froward Cape, Almirantazgo Sound and Inútil Bay
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
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accounted for 65% of the total abundance of M. rosea, whereas the lowest values were
detected in the Beagle Channel (<4%). All inhabited area corresponds to an oxygenated
estuary (Oximax or normoxic regime; 7.6 ± 2.4 mL O2 L-1). Given the abundance of M.
rosea and its recurrence in the Magellan neuston, we suggest search the ecological
functions of this copepod as well as its role as monitoring tool of process of pelagic
transport, retention and dispersal in other estuarine neustonic communities of southern
Chile. A preliminary description of composition of this neustonic “Magellan estuarine
snow” is established.
Keywords: Copepoda, neuston, sub Antarctic zooplankton, estuaries, Oximax zone.
Abundancia y distribución espacial de copepoditos neustónicos de
Microsetella rosea (Harpacticoida: Ectinosomatidae) en la costa occidental de
Magallanes, Chile (Crucero CIMAR 16 Fiordos)
RESUMEN. El copépodo harpacticoideo pelágico Microstella rosea habita la costa fría
templada de Sudamérica, desconociéndose la biología poblacional y su papel en el
neuston del sur de Chile. Durante el crucero CIMAR 16 Fiordos (octubre 11/Noviembre
19, 2010; 52º50 de 55º00; margen occidental de Magallanes), se recolectaron 26 muestras
(profundidad: 0-30 cm), para analizar la abundancia, distribución espacial y los
requerimientos oceanográficos de los copepodites (temperatura, salinidad y oxígeno
disuelto; < 1 m). M. rosea (700-1.000 µm LC) es la especie más abundante entre los taxa
holoneustónicos (30%), estuvo presente en toda la zona y fue 0.5 veces más abundantes
que los copépodos calanoídeos. Los copepoditos habitan aguas superficiales cuyas
temperaturas fluctuaron entre 6.5-8.5oC, con la máxima abundancia (1.000-10.000
individuos/5 minutos arrastre horizontal) en zonas con temperatura de 7,2 ± 0.7ºC; se
recolectaron en aguas de salinidad variable entre 26-33 psu (promedio = 29,8 ± 4.1), con
la abundancia máxima entre 29-31 psu. Cabo Froward, Seno Almirantazgo y Bahía Inútil
acumularon el 65% de la abundancia total de copepoditos; inversamente, valores menores
se detectaron en el Canal Beagle (< 4%). Toda la zona corresponde a un estuario
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
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oxigenado (régimen Oximax o normóxico). Dada la abundancia de M. rosea y su
recurrencia en esta zona, se sugiere investigar otras comunidades estuarinas neustónicas
de la zona de fiordos y canales del sur de Chile, como tambíén otras funciones ecológicas
desarrolladas por este copépodo harpacticoideo pelágico. Se caracteriza la composición
de la "nieve estuarina magallánica" y, en forma preliminar, se analiza el papel de la capa
neustónica en procesos de transporte, agregación y dispersión pelagica del plankton
austral.
Palabras clave: Copepoda, Neuston, zooplancton sub Antárctico,
estuarios, zonas
Oximax.
INTRODUCTION
Harpacticoid copepods are primarily benthic crustacean. A small proportion (< 0.5%) of
harpacticoid species inhabits the pelagic realm during throughout their life (Boxshall,
1979; Uye et al., 2002). These pelagic harpacticoids have relatively active swimming
ability, unique structural features such as an elongated worm-like body and either caudal
setae that delay or slow their sinking velocity (Microsetella spp & Macrosetella spp) or a
close
association
with
floating substrates
(e.g.
the
colonial
cyanobacterium
Trichodesmium; Calef & Grice, 1966; Tokioka & Bieri, 1966; O’Neil, 1998).
Additionally, it has been reported that a member of the genus Microsetella live on
aggregated and suspended organic matter (Alldredge, 1972; Ohtsuka et al., 1993; Green
& Dagg, 1997; Uye et al., 2002; Zaitsev, 2005).
Microsetella rosea is widely distributed in the sub Antarctic waters from southern
end of South America (5 to 10°C) to western Antarctic waters, as well as in the
subtropical warm waters of the South China Sea, the Mediterranean Sea and the Black
Sea (http://copepodes.obs-banyuls.fr). Adult females can reach a weight of 0.02 mg (dry
weight) and a maximum length of <800 µm. Members of this genus are numerically
dominant and attain high levels of abundance in marine neustonic communities,
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
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especially in coastal waters (Anraku, 1975; Dugas & Koslow, 1984; Uye et al., 2002;
Zaitsev, 2005).
Compared to the vast information available on population dynamics and
production of marine planktonic calanoids, few studies focus on marine and estuarine
planktonic non-calanoids, particularly on the genus Microsetella (Paffenhöffer, 1993;
Sabatini & Kiørboe, 1994; Uye & Sano, 1995; Uye et al., 2002). Uye et al. (2002)
studied the population dynamics and production of M. norvegica in the inland Sea of
Japan and found that reproductive activity occurs in early fall and that brooding sacs
reached a maximum of 16 eggs/sac. Under laboratory conditions, the total development
time took about a month to develop of eggs to adult at 20°C and half of this time at 27°C
(Uye et al., 2002). These pelagic harpacticoid attain high population abundance (7 x 104
ind. m-3) with a maximum production rate of 4.9 mg C m-3 day-1 in October. During the
winter, nauplii and copepodites disappear in December and the overwintering population
is dominantly composed of adults, primarily large females (Uye et al., 2002).
Hardy (2005) emphasized that biodiversity levels and densities of neustonic
organisms and how they vary spatially and temporally remain unknown as well as their
role in sustaining biogeochemical cycling and as source of nutritional requirements for
important trophic web in significant areas of the oceans. Given the lack of knowledge on
the neustonic communities along the Chilean coast (Palma & Kaiser, 1993), the present
research was originally proposed as to describe the community structure and biodiversity
of neuston in southern Chile.
The reason for focusing research efforts on this section of the water column are: i)
the neuston represents the boundary region of the air/water interface, and which can be
thought of as the ocean’s skin, given that it is only a few centimeters (Hardy, 1991;
Upstill-Goddard et al., 2003), thick and covers 71% of the planet’s surface, making it the
largest ecosystem in the world; and ii) in order to understand how the neuston is
influenced by environmental and oceanographic factors, such as temperature, solar
radiation, marine pollution, salinity and density variations, effects of UV radiation,
acidification and increasing temperatures in the oceans, etc. (Hardy, 1991; Rodríguez et
al., 2000; Zaitzev, 2005).
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, namely fragmentation and transport of organic matter to greater depths, are not
understood (Zaitsev, 2005; Koski et al., 2007). In temperate zones, the neuston plays an
important trophic role as a food source for meso- and macro-zooplankton and is a key
component in the production of “marine snow” and the vertical transport of organic
material from the surface of the oceans to greater depths (Conte et al., 1998; Hays et al.,
2005; Zaitsev, 2005; Koski et al., 2007).
The importance of the neuston layer in the early life cycle as well as in the larval
stages of commercially valuable species or species with ecological interest in Chile (e.g.
the snail Concholepas concholepas; Di Salvo, 1988; Molinet et al., 2006; the snail
Argobuccinum pustulosum, Gallardo et al., 2012; and the snail Fusitriton magellanicus,
Cañete et al., 2012a), its role in larval dispersion (Scheltema, 1986; Gallardo et al., 2012;
Cañete et al., 2012a), its utility in long term studies analyzing the influence of pollution
on the neuston, as well as its role in sustain trophic requirements of numerous coastal
filter-feeding pelagic and benthic species are unknown. In the latter case, it is relevant
that in southern Chile there exists a significant amount of fresh water that could potential
stratify the water column, producing vertical patterns of neuston, with the organic matter
being capable of sustaining pelagic and benthic filter-feeders consumption (e.g. the
family Mytilidae can accumulate between 15 to 25 kg m-2 in rocky shores of the southern
Chile (Osorio, 2002; Hardy, 2005; Aldea, 2012; Cañete et al., 2014).
In the waters of the Magellan Strait, typical pelagic calanoid and cyclopoid
copepods have been previously studied (Marín & Antezana, 1985; Mazzocchi et al.,
1995; Hamamé & Antezana, 1999; Marín & Delgado, 2001), with scarce reference to the
pelagic harpacticoid such as of the genus Microsetella (Aguirre et al., 2012). However,
work on pelagic harpacticoids copepods has not been widely cited in both sides of South
American coast (Palma & Kaiser, 1993; Boltovskoy, 1999). Intensive seasonal study
carried out in the Beagle Channel off Ushuaia, Argentina, made no mention to the
presence of M. rosea in this location (Biancalana et al., 2007; Aguirre et al., 2012).
The present research was designed in order to: i) record the abundance and spatial
distribution of neustonic copepodites of M. rosea along of the west margin of the
Magellan Region, Chile; ii) connect these ecological patterns with oceanographic
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
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parameters (temperature, salinity and dissolved oxygen), in order to define conditions
where this species attain their population development, and iii) to establish a comparison
between Microsetella abundance and that of other holoplanktonic taxa collected during
the CIMAR 16 Fjord campaign (spring, 2010). It was important to select some neustonic
components that could be used as biotracer of physical process associated to transporting,
dispersal, connectivity or aggregation of the Magellan neustonic communities and give
preliminary evidences about of the composition of the “estuarine snow” collected in this
cruise.
MATERIAL AND METHODS
The sampling was conducted during the CIMAR 16 Fjords campaign (October 11 to
November 19, 2010). Areas covered include the western mouth of the Magellan Strait,
(stations 7-15) to the Beagle Channel (Navarino Island: stations 37-43). In the areas close
to Dawson Island, samples were primarily collected in the Almirantazgo Sound,
Whiteside Channel and Inútil Bay (stations 51-60). Additionally, the west area of the
channels and islands located towards the Pacific Ocean were included in the sampling
area (stations 27-35) (Fig. 1). The RV Abate Molina platform was used for sampling.
Originally, it was planned a sampling along the eastern margin of the Magellan Strait;
however, it was not possible due to rough weather conditions (stations 1-6; not showed in
Fig. 1). The spatial distribution of stations is based in previous cruise carried-out in
CIMAR 3 Fjords (1997), which is orientated to know the biological, chemical and
physical oceanography of different microbasins located along Magellan Strait and
Magellan/Fueguian channels (Antezana, 1999).
At each station, surface sampling was conducted with a neuston net (80 cm wide
and 30 cm deep) with a 50 µm mesh size zooplankton net; this mesh net size was selected
because it has been used in other studies with small copepods studies (Kršinić, 1998).
This neustonic net consists of 4 lateral floats constructed of 3” diameter tubing and
weighs approximately 20 kg. The net was dragged along the surface (30-50 cm from the
surface) for 8 minutes at stations 7, 8 and 9. The speed of boat ranged between 1.5 and
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
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2.0 knots. However, given the high concentration of plankton collected, the time was
reduced to 5 min at all subsequent sampling sites. According to Hardy (2005) layer’s
classification system, the layer covered during the present study could correspond to
centilayer and surface layer (1 to 100 cm depth). Only one haul was conducted per
station. Samples were fixed with 5% neutralized formalin. Abundance and biomass data
was standardized to the number of individuals or wet-weight (g) per 5-minute drag due to
a lack of a flow-meter.
At each station, the vertical profile was performed with a rosette equipped with a
CTD Sea Bird that was deployed to different depths according to the bottom depth of
each site (Data Report CIMAR Fjords 16). Since the neuston is in the surface layer, data
on temperature, salinity and dissolved oxygen content was averaged between 1 and 2 m
of depth at each station.
In the laboratory, total sample was sieved on a 30 µm sieve for wet weight
determination and was expressed as biomass determination, including phytoneuston and
zooneuston together. Following the size ranges classification of neustonic organisms
proposed by Hardy (2005), in the present research we cover mainly micro- to
mesoneuston (20 µm a 20 mm size). Samples were divided with a Folsom fractioning to
1/8th of total content to facilitate counting of neustonic holoplankton and Microsetella
copepodites.
The copepod stages of Microsetella were identified following to Uye et al. (2002)
and accounted for all individuals present in each sample. In the present study, only
abundance data based on identification of copepodites was considered while other stages
of the life cycle of M. rosea were not included (nauplius and adults). Others components
of the zooplankton were identified based on Palma & Kaiser (1993) and Boltovskoy
(1999).
According to Davies & Slotwinski (2012) some criteria for identifying M. rosea
and for differentiating it from M. norvegica are: i) size, if over 0.8 mm it is likely M.
rosea; ii) length of caudal rami setae, if nearly twice as long as the body then it is M.
rosea, if shorter than it could be either species (setae could be broken); iii) M. rosea has
spinules on the metasome and urosome, M. norvegica has spinules on the urosome; iv) M.
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
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norvegica caudal rami are slightly more divergent than M. rosea; and v) M. rosea may be
pink in color. Both species has cited to Chilean coast (Pacheco et al., 2013).
Samples were stored at the Laboratorio de Oceanografía Biológica Austral
(LOBA), Department of Sciences & Natural Resources, Faculty of Sciences, Universidad
de Magallanes, Punta Arenas, Chile.
A Kruskal-Wallis non-parametric test was used to search different trends in
abundance of Microsetella to search potential differences between four main geographic
zones located along of the west margin of the Magellan Region (Magellan and Fuegian
channels; Antezana, 1999) (Zar, 1999). The relationship between the abundance of
copepodites of M. rosea with the oceanographic parameters, physical (temperature) and
chemical (salinity and dissolved oxygen), were tested using the non-parametric
Spearman’s Rank-Order correlation coefficient (rs) (Daniel, 2000; Zar, 1999).
The Magellan planktonic organisms represents bio-models to search distributional
trends associated with bio-physical interactions in estuarine ecosystems: firstly, to the
study the thin neustonic layer reduce the number of spatial components (x, y) and avoid
constraints associated to the vertical water stratification; secondly, the sampling spatial
scale include a meso-scale pattern (10-1000 km; Mann & Lazier, 1991; Garçon, 2001),
and thirdly, the area represent a natural laboratory where to study the population dynamic
of plankton in a heterogeneous coastal system (Downing, 1991).
In order to classify the type of distribution spatial of the copepodites of M. rosea
in the study area, a dispersal index (Id) was applied. This index is based in the variance to
mean ratio (s2/x̅) and describes a trend of the spatial distribution. If an Id = 1.0 represents
a random distribution (s2 = x̅); if Id < 1, an uniform or regular distribution (s2 < x̅), while
that if Id > 1, a clumped distribution (s2 > x̅) (Ludwig & Reynolds, 1988; Hulbert, 1990).
RESULTS
Oceanography
The spatial variability of three oceanographic factors (temperature, salinity and dissolved
oxygen) was measured in the surface layers in stations analyzed during research
expedition (Table 1).
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
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Water temperature fluctuated between 6.16 (St 52) and 8.42oC (St 56), with an
average water temperature of 7.2 ± 0.59oC in the study area (± = standard deviation). The
highest water temperatures were detected in Whiteside Channel and in Inútil Bay, while
the lowest temperatures were detected along the eastern side of the Magellan Strait and in
the interior of Almirantazgo Sound, near the glaciers discharge of the Darwin Ice Field
(Table 1).
Of the three oceanographic variables measured, salinity varied widely, ranging
from 28.897 (St 10) to 32.777 psu, with an average value of 30.7 ± 0.91 (Table 1). Based
on the classification criteria for estuarine conditions of southern Chile proposed by
Valdenegro & Silva (2003), all samples in the study area were taken in Estuarine Waters
(EW; 1-32) or in Modified Subantarctic Water (ASAAM; 32-33). These last values were
recorded out of Magellan/Fuegian channels.
Dissolved oxygen content ranged from 6.655 (St 15) to 8.27 mL O2 L-1 (St 55)
seawater, with an average value of 7.4 ± 0.35 mL O2 L-1. The surface layer was
oxygenated throughout the study area, with a maximum value in a glaciated area of
Almirantazgo Sound. According to Cañete et al. (2012b), the area surveyed would be
classified as Oximax or normoxic condition (oxygen maximum zone; values > 2 mL O2
L-1) (Table 1).
Neustonic biomass/abundance
The neustonic biomass collected fluctuated by up to two orders of magnitude, ranging
from 0.7 (st 39) and 31.89 g 5min-1 of horizontal drag (Mhd) (St 52), with an average of
8.55 ± 7.33 g 5Mhd (Fig. 2). The neustonic biomass was highest in protected areas such
as Froward Cape/Almirantazgo Sound/Inútil Bay (average = 12.3 g 5Mhd-1) and along
the west arm of the Magellan Strait (between Capitán Aracena island and the west mouth
of Magellan Strait) (average = 11.1 g 5Mhd-1), and lowest along the Beagle Channel (5.5
g Mhd-1) (Table 2).
The spatial pattern of the neustonic abundance followed a trend similar to the
biomass, with maximum values in the Almirantazgo/Inútil Bay area (average = 18,350
ind 5Mhd-1and lowest abundance in the Beagle Channel (average = 3,358 ind 5Mhd-1).
The average abundance in those stations located between west side of the Dawson Island
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
10
and the Pacific Ocean and along the occidental arm of the Magellan Strait varied between
7,172 and 7,337 ind 5Mhd-1 (Tabla 2). In all study area, the average abundance of
neuston was 9,179 ± 10,281 ind 5Mhd-1, indicative of a patchy distribution with a
variation coefficient of 112% (Fig. 3).
Abundance of the copepod Microsetella rosea
The copepodites of M. rosea were collected in all study area (Fig. 3). However, there are
evident differences between zones, indicating wide spatial variability within west margin
of the Magellan Region. For example, in the Almirantazgo Sound/Inútil Bay/Paso Ancho
zone/Froward Cape (mid Magellan Strait) it was recorded the maximum abundance of M.
rosea, while the lowest abundance was recorded in stations along Beagle Channel and in
open areas around Navarino Island with only 362 ind. 5Mhd (Table 2).
In total, copepodites accounted for 30% of the total abundance of neustonic taxa
(238,673 ind) (Table 3). The zone Almirantazgo Sound/Inútil Bay/Paso Ancho
zone/Froward Cape accounted for 61.5% of the total abundance of M. rosea, while the
lowest values were detected in Beagle Channel (<4%). The west margin of the Magellan
Strait accounted near to 25% and the zone western to the Dawson Island to the 10% of
the total abundance of copepodites of M. rosea (Fig. 3). The abundance of M. rosea
copepodites showed a geographic trend in terms of abundance, with significant
differences mostly between Paso Ancho microbasin and Beagle or Fuegian Channels
(Antezana, 1999) (Table 2).
This study revealed that the distribution pattern of copepodites of M. setella
shows variations to four orders of magnitude. This type of spatial distribution pattern can
be classified as clumped o aggregated (Ludwig & Reynold, 1988; Hulbert, 1990;
Downing, 1991), which is in according with the spatial distribution of copepodites along
west margin of Magellan Region (Fig. 4a & 4b). Similar trend was observed in the total
neustonic abundance and biomass (Table 2).
Oceanography and features of the neustonic habitat of Microsetella rosea
copepodites
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
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In the present study, the copepodites of M. rosea inhabit the neustonic layer with
temperatures ranging between 6.5 (St 40) - 8.4°C (St 56), with maximum abundance
(1,000 to 10,000 ind 5Mhd-1) only detected in Sts 7, 55 and 60 (surface temperature
ranged between 6.79 and 7.69ºC). However, the Spearman correlation coefficient
between sea surface temperature and abundance of copepodites of M. rosea produce a
significant, negative trend between both parameters (rs = -0.36; p < 0.05; N = 26) (Table
1; Fig. 2 & 3). The average and standard deviation of copepodites abundance was 2,761 ±
4,278.
Additionally, copepodites were found at stations with salinity levels between
28.897 (St 10) and 32.777 psu (St 15) (mean = 30.7 ± 0.9 psu), with the highest
abundance found in waters with salinity levels between 30.37 (St 55) and 30.53 psu (St
7). The relationship between salinity and the abundance of copepodites produce a
significant, positive trend between both variables (rs = 0.22; p < 0.05; N = 26). The area
inhabited by M. rosea is classified as an oxygenated estuary (mean = 7.4 ± 0.4 ml O2 L-1)
(Table 1). It was found a significant, negative relationship between the content of
dissolved oxygen and the abundance of M. rosea in Magellan waters (rs = -0.19; p < 0.05;
N = 26).
Overall, given the limited range of variation of these three oceanographic
variables at the stations where the M. rosea was found, it can be concluded that this
pelagic harpacticoid copepod is adapted to estuarine environmental conditions. This
situation are found along of the west margin of the Magellan Region and within of
Magellan Strait limits. Within of the Magellan Strait is abundant in waters enclosed in the
Paso Ancho-Forward Cape channel or around of the Dawson Island (Fig. 3).
Contribution of M. rosea in comparison to the rest of the neuston
During the CIMAR 16 Fjords cruise, 238,673 individuals were counted from the
neustonic meroplankton and holoplankton taxa (41.27% and 50.98%, respectively) (Table
3). Within the holoneustonic taxa, calanoid and harpacticoid copepods were the most
abundant, including M. rosea. The abundance of copepodites of M. rosea was near twice
superior respect to calanoid copepods (Table 3). An important fraction of juvenile of
appendicularian was collected (4.3%).
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
12
Within meroneustonic taxa, the numerically dominant group included the mytilid
larvae (21.12%), followed of the unidentified larvae of a polychaete of the family
Polygordiidae (16.5%) and cyphonaute larvae (2.41%). Cypris of barnacle (0.61%) and
pluteus of echinoderms also were detected (Table 3). Decapod crustacean larvae were
scarce (<0.26%). A total of seven holo- and nine meroneustonic taxa could be used as
biotracer in the west Magellan region (Table 3).
Thus, holoplanktonic component of the neustonic communities numerically
dominate on the meroplanktonic taxa during spring oceanographic condition in the west
margin of Magellan region.
DISCUSSION
The present research was designed with the aim of i) to obtain a record of the abundance
and spatial distribution of neustonic copepodites of M. rosea along the west Magellan
Region, Chile; ii) to know the oceanographic requirements, and iii) to establish a
comparison between Microsetella abundance and that of others holoplanktonic taxa
collected onboard of the CIMAR 16 Fjord campaign (spring, 2010). It was important to
select some neustonic components that could be used as biotracer of physical process
associated to transporting, dispersal, connectivity or aggregation of the Magellan
neustonic communities and give preliminary evidences about of the composition of the
“estuarine snow” collected in this cruise.
Abundance and spatial distribution of M. rosea in Magellan waters
M. rosea is a pelagic, neustonic, harpacticoid copepod that inhabits the interior waters of
Magellan channels, at southern Chile (Razouls et al., 2005-2014), showing a spatially
population connected along west margin of Magellan Region. In the present study, it was
shown that this species inhabits surface waters within specific areas of the western
margin of the Magellan Region, Chile, where it can become the most numerically
dominant species of copepods as well as the most dominant taxa of the neustonic
community. M. rosea was distributed in all study area (Fig. 2, Table 2).
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
13
The Magellan neuston was composed of holoplanktonic and meroplanktonic
stages (Table 3). Shanks & Carmen (1997) indicate that larvae of polychaetes are
strongly associated with marine snow, whereas Shanks & Walters (1997) cited the
massive presence of holoplankton, meroplankton, and meiofauna associated with marine
snow. In the present study, M. rosea copepodites and the polychaete larvae named as
“Banana larvae” (recently has been identified as a potential Polygordiid exolarvae; P.
Ramey-Balci, com.pers.; Ramey-Balci & Ambler, 2014) were the most abundant
meroneustonic components. Larvae of Munida subrugosa dominated in relation to others
crustaceans, being less abundant respect to León et al. (2008) and Mujica et al. (2013) in
northern sections of the Chilean fjords and channels (Puerto Montt to San Rafael
Lagoon). A fraction of larvae of echinoderms and cyphonautes larvae of bryozoans were
detected being relatively recurrent in some specific neustonic samples (Table 3).
The population density of M. rosea in the neuston in inner channels within the
western sector of the Magellan Region (103-104 ind 5Mhd-1) is approximately one times
greater than that of calanoid pelagic copepods detected in this same project (Table 3).
Similar magnitudes of abundance were detected for the species M. norvegica in the
inland of Japan Sea (Uye et al., 2002), where the biomass can also reach up to 100 mg C
m-3 in the fall. By contrast, in the Adriatic Sea copepodites and adults of Microsetella spp
showed minor presence respect to Calanoid, Cyclopoid, oncaeid and oithonid copepods
(Kršinić & Grbeco, 2012).
One aspect not considered in the present study is the vertical distribution of the M.
rosea copepodites. The neustonic sampling only considered the vertical distribution in the
first 30 cm of this layer. However, a widest vertical sampling could demonstrate if this
species is distributed to deepest layers of the water column. Finally, it is worth nothing
that despite a long tradition of zooplankton studies in the Magellan Region, a review of
the taxonomic and ecologic works of Mazzocchi et al. (1995), Antezana (1999) and
Marín & Delgado (2001) revealed there is no reference to the presence of M. rosea in
copepod samples. However, Fernández-Severini & Hoffmeyer (2005) cited the presence
of diverse species of pelagic harpacticoid copepods around Beagle Channel during
summer condition.
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
14
The absence of M. rosea copepodites in Magellan waters in previous studies could
be due to large aperture size of mesh net. In our study, we use a mesh net of 50 µm while
that in other studies have cited sizes over 200 µm (Mazzocchi et al., 1995; Antezana,
1999; Defren-Janson et al., 1999; Marín & Delgado, 2001; Biancalana et al., 2007;
Guglielmo et al., 2014). Alternatively, it is possible that the copepodites live only in the
surface layers of water column and the horizontal drag could be a good mechanism to
collect abundant specimens; sampling strategies of previous studies has considered only
the vertical tow of the zooplanktonic net, which could to produce a lowest abundance of
this copepod (Kršinić & Grbec, 2012).
The spatial distribution and the levels of variability detected in neustonic
Microsetella population in the west margin of Magellan region, offer an interesting field
of research to analyze the relationship between physical processes as a primary
determinant of the dynamics of pelagic, estuarine ecosystems, providing the
environmental conditions and the physical structure within which the biological processes
occur (Mann & Lazier, 1991). Thus, neustonic communities and populations of this area
could to offer opportunities to study the meso-scale spatial variability on important
biological phenomena arising from the interaction among physical processes, physiology
and behavior of the estuarine neustonic organisms (Garçón et al., 2001).
Oceanographic requirements of Microsetella rosea copepodites
The spatial distribution of the neustonic communities can be influenced by diverse
environmental and oceanographic factors, such as temperature, solar radiation, marine
pollution, salinity and density variations, effects of UV radiation, acidification and
increasing temperatures in the oceans (Zaitzev, 2005). For this reason, knowing their
physiological requirements is important to explain the spatial distribution of estuarine
taxa. The area inhabited by M. rosea is classified as an oxygenated estuary (mean = 7.6 ±
2.4 mL O2 L-1) (Table 1), which correspond to an Oximax zone (> 4 mL O2 L-1; Cañete et
al., 2012b) or normoxic condition (> 2 mL O2 L-1; Tyson & Pearson, 1991).
Considering the wide amplitude of variation of the surface salinity in the
Magellan Region ranged between 0 to 32 psu (Valdenegro & Silva, 2003; Palma et al.,
2014b), the close range of haline conditions detected during the present study could to
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
15
suggest a stenohaline behavior of M. rosea copepodites. New experimental studies on the
physiological response to these oceanographic parameters as well as to thermal
requirements will be necessary to confirm it.
It relevant made mention that the wide conditions of salinity detected in the
southern Chilean fjord and channels system could to offer a natural laboratory to study
the effects of different salinities on the larval ontogenetic behavior. Previously, León et
al. (2008) showed that most larval stages of the squat lobster Munida gregaria were
temperature-dependent, and that the salinity range of the youngest zoea was wider than
that of oldest larvae and post-larvae, coinciding with an ontogenetic distributional change
from estuary to oceanic stations on the shelf; similar situation has been detected in other
pelagic taxa such as Siphonophora living in cold waters of southern Chile (Palma et al.,
2014a). This variable shows scarce variation along west margin of Magellan Region in
comparison of other fjord zones of the southern Chile (Pickard et al., 1980; Silva &
Palma, 2008; Sievers & Silva, 2010; Palma et al., 2014a).
The spatial distribution of M. rosea in the west margin of the Magellan Region
seems be regulated by changes in salinity, such as other members of the genus
Microsetella. Yamazi (1956) found that M. norvergica inhabits areas near the mouths of
bays rather than sites close to river mouths or other freshwater inputs. Uye & Liang
(1998) found that in the inland Japan Sea, M. norvegica has a low population density in
water with salinity levels <30 psu. Uye et al. (2002) indicate that M. norvegica is a
stenohaline species that does not tolerate large variations in salinity. M. rosea reaches
greater numbers in waters with salinity ranged between 29 and 31 psu in Magellan waters
(Figure 4b). Salinities >31 psu found along Beagle Channel seem not be optimal for M.
rosea due to low abundance detected.
Similar situation was found for M. norvegica in the Beagle Channel by Aguirre et
al. (2012), detecting presence around of the year with abundances between 0.1 and 66.0
ind m-3. The difference of abundance of both species of Microsetella in the Beagle
Channel could be due to that Aguirre et al. (2012) developed their study near to M.
pyrifera kelp bed, while that during CIMAR 16 Fjord the sampling stations were located
in the center of each channel or in open waters.
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
16
Guglielmo et al. (2014) describes the composition and abundance of
holoplanktonic polychaetes in Magellan waters where only some species seem be
affected
by
salinity
(spatial
distribution
and
abundance
of
Pelagobia
longicirrata and Tomopteris planktonis were negatively related to chlorophyll-a, and
positively affected by salinity, respectively).
The spatial distribution of M. rosea seems not affected by dissolved oxygen in
west Magellan waters (Table 2). The study area can be classified as an oxic (facies),
aerobic (biofacies) and normoxic (physiological) conditions, following the recommended
terminology for oxygen regimes and the resulting biofacies in marine environments (2 to
8 mL O2 L-1; Tyson & Pearson, 1991). Oxygen in subantarctic waters showed not biolimitation in the water column of different micro-basin in the Magellan Region
(Valdenegro & Silva, 2003). Cañete et al. (2012b) has incorporated the term Oximax to
made reference to oxygenated waters of southern cold temperate latitudes. To evaluate
the effects of the normoxic vs hypoxic (2 to 0.2 mL O2 L-1) and anoxic (< 0.2 mL O2 L-1)
regimes (Tyson & Pearson, 1991) on the neustonic communities and the abundance of M.
rosea copepodites it will need to sample other Magellan micro-basins with less dissolved
oxygen or to select coastal zones with important signs of estuarine eutrophication and
organic matter enrichment such as mouth of important rivers.
Microsetella abundance versus others holoplanktonic taxa in Magellan waters
There are scarce comparative studies on the mesozooplankton in estuarine Magellan
waters. During the Joint Chilean-German-Italian Magellan "Victor Hensen" campaign
(November 1994), distributional pattern was studied and community analyses of
mesozooplankton were made at seven stations in the Magellan region (Defren-Janson et
al., 1999). They detect: i) a high number of individuals were collected in the area
Magdalena to Brecknock Channels, at stations with a mixed water column. In the
southern part (Beagle and Ballenero Channels), low zooplankton abundance were
associated with a stratified water column due to melt water from several glaciers.
Contrary to our study, in the spring 1994 the holoplankton dominated the assemblages
(83-97%), where the copepods were by far the most abundant taxon, contributing to more
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
17
than 2/3 of the total zooplankton numbers. They did not make reference to the presence
of Microsetella in these samples.
Patches of abundance of small copepods could to be influenced by frontal zone
(Zervoudaki et al., 2007). In the west Magellan Region is common the presence of frontal
zones detected by accumulation of ice, detached macroalgae as Macrocystis pyrifera
kelp, changes of color of surface waters and accumulation of foam in the surface layer
(Valle-Levinson et al., 2006). The high abundance (1,000-10,000 ind 5Mhd-1) in some
stations of the CIMAR 16 Fjords, specially around Dawson Island could be due to the
presence of frontal zones given the wide difference between stations in the abundance of
M. rosea copepodites (Fig. 4a y 4b) or deepest sill in the Whiteside Channel (Palma et al.,
2014b).
However, we need to analyze others meteorological and oceanographic and
topographic variables to explain patterns of abundance and spatial distributional of the
Magellan neuston (Owen, 1989). It is relevant to know those oceanographical conditions
that produce aggregation, dispersal and transport of small plankton in the Magellan
pelagic environments. Important will be to maintain news neustonic sampling programs
around Dawson Island due the high concentration detected in the eastern end (Fig. 2 & 3),
which could be related to the “island wake effect” and most protected coast from
predominant spring winds (Mann & Lazier, 1991).
During the present study was detected that temperature, salinity and dissolved
oxygen showed a regular or uniform spatial distribution in the west margin of Magellan
Region while that the total neustonic biomass and abundance as well as the abundance of
Microsetella showed a clumped or aggregated spatial distribution (Tables 1 & 2). We
propose that this contrasting trend between environment and neustonic communities
could to mean that in the channel sections around Dawson Island could predominates the
retention or processes of pelagic aggregation.
Kršinić & Grbeco (2012) indicates that the copepodites of the harpacticoids
Microsetella norvegica and M. rosea are dominant in the euphotic zone of the Adriatic
Sea (1 to 5 m depth), where pelagic harpacticoids represented an average of 4.4% of the
total number of copepodites and adult copepods from the surface to a depth of 50 m while
that was of 6.7% between 50 and 100 m depths. In this case, harpacticoid abundance
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
18
shown a patchy spatial pattern, with a maximum of 1,800 ind m-3 sampled at a depth of
20 m and dominated by Microsetella norvegica and M. rosea. The highest average
harpacticoid abundance (450 ind m-3) was recorded during summer season, representing
24% of the total number of copepodites and adult copepods.
Microsetella rosea and the composition of Magellan estuarine snow
One of the adaptive strategies deployed by pelagic harpacticoid copepods is their ability
to attach and hold onto particulate organic matter floating and dispersed in the water
column, which acts as a means of transport, and in turn as a source of food available in
the surface layers of the ocean. The fragmentation of this material by Microsetella
reduces its size/weight allowing its consumption by other smaller microphages, and
through the production of fecal pellets and the shedding of its shell, it can make a
significant carbon contribution to the surface as well as deeper zones (Lampitt, et al.,
1993; Uye et al., 2002; Kiørboe, 2000). Particularly, is important the formation and fate
of marine snow due to the change in the structure of organic matter produced in thin
layers of water column, having large-scale or global implications (Kiørboe, 2001).
Other types of organism that could aid in diversifying the sources of organic
particulate matter present in the neuston samples collected aboard the CIMAR 16 Fjords
include microalgae, particularly diatoms forming chains as well as some dinoflagellates.
Cañete et al. (2013a) found that some phytoneustonic samples had a biodiversity of 33
species of diatoms and 35 species of dinoflagellates, and one species of silicoflagellata. In
total, 74 species were collected. However, many Magellan phytoplankton cells show
large size, suggesting than M. rosea could to sustain their feeding on micro- or
nanoplankton, debris, mucous or cells with <20 µm diameter due to their small size of
mouth. According to Alvés de Souza et al. (2008) some functional groups or guilds of the
marine/estuarine phytoplankton assemblages collected in the southern Chile is composed
of about 131 species; 74% of these species are diatoms, 19% dinoflagellates and 7%
nanoflagellates. Thus, in reference to this paper, the neustonic phytoplankton collected in
the CIMAR 16 fjords formed chains, have large diversity of shape cells with many spines
and could be classified as R-strategist.
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
19
Other aspect that could explain the actual spatial pattern of Microsetella
copepodites is the spatial distribution of chlorophyll-a, where is possible to detect four
stages of production along the western Magellan margin (Hamamé & Antezana, 1999) in
relation to salinity, temperature and stratification of water column. These stages are: i) in
Paso Ancho- Magdalena Sound showed a shallow chlorophyll maximum (ca. 5 mg m-3 at
0-20 m) in a vertically homogeneous cold and brackish water column; ii) in the section
Magdalena, Cockburn and Brecknock channels had relatively lower chlorophyll
concentrations (2-3 mg m-3 at 0-50 m), minor stratification of salinity and a surface lens
of warmer water with direct Pacific Ocean influence; iii) in the Ballenero Channel-Nordwestern arm of Magellan Strait had a subsurface layer of high chlorophyll concentration
(>4 mg m-3) in a vertically stratified water column of two salinity layers and three
temperature layers; and, iv) in the Beagle Channel presented a subsurface chlorophyll
maximum (>4 mg m-3) extending to the bottom, and vertically homogeneous salinity and
temperature distribution. In our case, the maximum abundance of M. rosea was recorded
in the zone Paso Ancho-Magdalena Sound, including the zone of Froward Cape (Fig. 3).
However, some preliminary antecedents of nutrients availability around stations
located between Almirantazgo Sound and Inutil Bay during CIMAR 16 Fjords, indicate
that the area with higher abundance of Microsetella could be classified as oligotrophic
considering the low values of phosphate (<0.5 µM), nitrate (<2 µM) and silicates (<1
µM) (Vargas et al., 2011).
Members of genus Microsetella seem be omnivorous because their diet including
abandoned larvacean houses (Alldredge, 1972, 1975 & 2005; Vargas et al., 2002),
“macroscopic aggregates of marine snow” (Alldredge & Youngbluth, 1985), including
diatoms debris (Alldredge & Gotschalk, 1988; Alldredge & Silver, 1988), conforming a
pelagic fragmented habitat (Atmar & Patterson, 1993). In the present study, we collect
appendicularian specimens in only 13 stations in the west margin of the Magellan Region
(Table 3), but not evidence of trophic relationship between both taxa were observed.
Other roles played by the neustonic layer in Magellan waters
Cañete et al. (2015, in litteris) in a small embayment of the Magellan Region, has also
observed that the neustonic zone may represent an important route for the transport and
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
20
dispersion of subantarctic meroplankton and juveniles stages of bivalves. Recently, levels
of 103 to 104 pelagic juveniles of the brooder clam, Gaimardia trapesina, have been
detected in the interior of Porvenir Bay. In the last case, it would be possible to postulate
that this bivalve, possess other dispersal strategies apart from the traditional rafting on the
M. pyrifera kelp (Edgard, 1987; Highsmith, 1985; Hellmuth et al., 1994; Thiel, 2003;
Thiel & Gutow, 2005). In the present study, the presence of large abundance of larvae of
Polygordiid polychaete, cyphonautes of bryozoans, echinoids and some decapods
crustacean confirm this role (Table 3).
Cañete et al. (2013b) point out that in the Magellan channels the adults of the
benthic polychaete Platynereis australis attain pelagic behavior during reproductive
maturation allowing it to also adopt diverse strategies of pelagic transport through their
pelagic adult stages, in addition to gametes and larval transport. Thus, it is postulated that
some benthic invertebrates of Magellan estuaries could to display a diverse array of
dispersal strategies using temporally the neustonic layer, in response to the large island
fragmentation landscape and the patch habitat of the kelp M. pyrifera. Other typical
example of pelagic schooling behavior is showed by the crustacean Munida subrugosa in
the channels from southern Chile, which shows swimming behavior of juveniles and
adults specimens (León et al., 2008).
Due to the presence of at least 26 taxa represented by their larvae in the western
Magellan neuston (Table 4), the larval transport through this layer could to have
important biological implications for direct effects of tides, winds and currents, on the
aggregation and dispersal of this mero- and holoneuston, producing biogeographic and
biodiversity affinities between Atlantic and Pacific coast of the Magellan Region (Gaines
et al., 2007; Tilburg et al., 2012). The large number of larval stages in the west Magellan
neustonic samples is coincident with the spring spawning cycle and phenological
reproductive behavior of some Magellan gastropods, echinoderms and crustaceans
(Oyarzún et al., 1999; Fernández-Severini & Hoffmeyer , 2005; Aguirre et al., 2012;
Cañete et al., 2012a).
Future studies could to probe how the neustonic layer could to be able to sustain
larval connectivity between different benthic and planktonic populations in both sides of
the Magellan region (Pineda et al., 2007). The most frequently winds are one-directional
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
21
and are affected by the influence of the West Wind Drift Currents directed to West to
East along of the sub Antarctic Circle (Fell, 1962; Leese et al., 2010). Molecular
evidence of the addressing of the mutational changes in the Magellan limpet Nacella
magellanica (González-Wevar et al., 2012) and in a species of isopod (Leese et al., 2010)
suggest a West-East trend in the dispersal pattern around Magellan Region.
Another aspect that should be investigated is the ability of M. rosea, and other
members of this genus, to preserve the normal behavior of harpacticoid copepods that
inhabit the benthos. Recently, Pacheco et al. (2013) detected two species of Microsetella
in the subtidal soft bottom zones in northern Chile emerging from the sediment into the
water column defined as diel migration. Therefore, it is possible that spatial variations in
the abundance of the copepod M. rosea in the Magellan Region could be affected by
sampling time (day/night) and the depth of the stations. However, all stations sampled
during CIMAR 16 Fjords are deeper than 32 m, attaining down to 1,120 m depth (Table
1). The potential origin of the neustonic population of M. rosea in Magellan waters could
be supplied by shallow waters areas supplied through horizontal transport.
Others roles of the neustonic harpaticoids are as preys. Green & Dagg (1997)
made reference to the value of the mesozooplankton association with medium to large
marine snow aggregates in the northern Gulf of Mexico. Also, neustonic cyclopoids
could to retard the vertical flux of zooplankton faecal material through recycling
(González & Smetacek, 1994).
In addition, we need to verify the importance of the neuston as a biological tracer
of small-scale biophysical processes in coastal marine waters as well as to study
latitudinal variation in the southern Chilean coast. In our study, not direct relationship
between salinity and the M. rosea abundance was observed (Table 2). This situation
could be associated to that in the surface Magellan waters sampled during CIMAR 16
Fjord there is close range of variations in temperature and salinity. Cañete et al. (2013b)
demonstrate that in neustonic samples collected during CIMAR 18 Fjord (winter, 2012)
carried-out between Guafo Channel and Elephant Estuary, southern Chile, there is a
positive and significant lineal relationship between the salinity and abundance and
biomass of neuston (range of salinity between 5 and 33 psu). This fact could to
incorporate to the neuston as an important oceanographic monitoring tool to track the
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
22
estuarine, diluted waters into inner channels off southern Chile (Palma et al., 2014a).
Previously, Johan et al. (2012) have detected that the spatial distribution of copepods
follow the salinity gradient in the tropical estuary of Perai River, Malaysia.
The actual spatial pattern of the estuarine neustonic communities from Magellan
waters could be modified if the ice melting and rainy conditions change in direct
relationship to global warming in the southern Chilean coast. Therefore, a permanent
monitoring of subantarctic neustonic communities could be highly recommended.
ACKNOWLEDGEMENTS
The authors would like to thank to the Servicio Hidrográfico y Oceanográfico de la
Armada (SHOA, Chile) and the financial support to this project (CONA C16F 10-014),
as well as to RV Abate Molina crew, Instituto de Fomento Pesquero, Chile (IFOP), for
providing the facilities necessary to collect neustonic samples during the CIMAR 16
Fjord cruise, We would also like to thank the Program GAIA Antártica (MAG1203),
Contract MINEDUC-UMAG, for supporting the translation of the original manuscript.
Special thanks to the Programs CIMAR 18 and CIMAR 20 for providing partial funds to
support this publication. Special thanks to Ms. Sc. Jaime Ojeda for collection of these
neustonic samples during CIMAR 16 Fjord campaign. We thank the identification of
neustonic phytoplankton by Ms. Sc. Cristian Garrido (IFOP, Chile). This manuscript was
partially funded by UMAG Research Program N° PR-F2-01CRN-12.
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33
Table 1. Surface oceanographic data (average between 1 and 2 m depth) from CIMAR 16
Fjord cruise (October-November 2010) at stations where neustonic samples were
collected in the western 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
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
34
Table 2. General summary of the total neustonic biomass and abundance as well as the
total abundance of the copepod Microsetella rosea collected in the CIMAR 16 Fjords
campaign in 4 macrozones located in the west margin of the Magellan Region, Chile
(October-November 2010). Average values ± standard deviation. Mhd = minutes of
horizontal drag. Significant differences were detected between macrozones based in
Kruskal-Wallis test (F 3, 25 = 8.63; p > 0.05).
Macrozones
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)
12.4 ± 9.4
18,350 ± 11,594
6,307 ± 5,993*
6.7 ± 8.2
7,172 ± 3,888
2,225 ± 3,693*
4.7 ± 2.7
7,337 ± 5,263
1,210 ± 1,226*
3,358 ± 4,321
342± 264 *
5.8 ± 3.2
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
35
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
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
36
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 copepod Microsetella rosea in the west margin of the
Magellan Region, Chile (October-November, 2010).
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
37
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
Stations
Neustonic biomass
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). The average and standard deviation of neustonic biomass and abundance were
8.55 ± 7.33 and 9,179 ± 10,281, respectively. To the original data of abundance was
applied the function log (x + 1) to obtain only values > 0 in the axe.
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
38
Figure 3. Spatial distribution of copepodites of the pelagic harpacticoid Microsetella
rosea in the west margin of Magellan Region, southern Chile (spring, 2010). Abundance
expressed as ind 5Mhd-1 (minutes of horizontal dragging). The average and standard
deviation of copepodites abundance was 2,761 ± 4,278.
Abundance and distribution of a neustonic copepod in Magellan waters, Chile.
Total abundance Microsetella
(log)
39
100000
N = 26
10000
1000
100
10
1
5
6
7
8
9
Sea surface temperature (ºC)
10
Total abundance Microsetella
(Ind./sample (log-scale)
100000
N = 26
10000
1000
100
10
1
25
27
29
31
33
Sea surface salinity (psu)
Figure 4. Temperature and salinity of the neustonic layer analyzed during the CIMAR 16
Fjords cruise (spring, 2010) to determine the oceanographic requirements of Microsetella
rosea copepodites. Abundance expressed as ind 5Mhd-1. The average temperature and
salinity of neustonic layer in the study area was 7.2 ± 0.59°C and 30.7 ± 0.91 psu.