NOTES
DATE
ACCEP1ED: June
ADDRESS:
I,
707
1994.
Harbor Branch Oceanographic Institution, 5600 North U.S. Highway J, Fort Pierce, Florida
34946.
BULLETIN OF MARINE SCIENCE, 56(2): 707-710,
1995
MERCURIAL POLLUTION IN THE SEAGRASS
TESTUDINUM (BANKS EX KONING)
THALASSIA
Daisy Perez
Mercurial pollution in Venezuela's coastal area has been demonstrated for several years, especially at the Golfo Triste region, Parra (1974) suggested that sediments in Cafio Alpargaton were polluted by mercury, at levels exceeding 3 ppm.
This water course served as a collector of waste lagoons from a Petrochemical
Complex operating since 1956 up to 1976, producing NaOH and HCl through an
electrolytic process using metallic mercury electrodes. Previous reports on this
subject indicated significant levels of mercury found in some marine organisms,
like sea stars (Iglesias and Penchaszadeh, 1983) and several fish species (Monaco
and Ozaeta, 1979; Urich, 1981; Ishizaki and Urich, 1985).
Given the great importance that seagrass communities have in coastal ecosystems, it is necessary to know the present degree of mercurial pollution in seagrasses bordering the mercury disposal area. A key objective of this work was to
assess the mercurial concentration in water, sediment samples and in Thalassia
testudinum, collected from the polluted zones. These results have been compared
to the concentrations in samples taken from a mercury-free coastal zone, considered as baseline data.
METIfODS
Thalassia testudinum was sampled at times and locations detailed below, selecting whole and undamaged plants, with similar size and general appearance. At the same time, sediment and water
samples were collected.
Collecting Stations.-Punta
Mor6n: IQo30'00"N, 68°06'48'W, located in the central zone of the Golfo
Triste, is characterized by a regular, low and sandy beach. Thalassia testudinum seagrass beds are
between 20 em and 1.5 m deep.
Cayo Animas: IQo49'00"N, 68°15'48'W, located in the Morrocoy National Park, is a complex system
of water bodies interconnected by channels, surrounding islets or small islands made up of mangrove
swamps. Coral reefs and beds of seagrasses of T. testudinum are frequent. Cayo Animas seagrass is
also present at depths from 50 em to 2 m.
Los Totumos Bay: IQo33'20"N, 66°02'56"W, located east of Codera Cape, between Punta Crucecita
and Punta Castillito is a 300 m coastal bay, surrounded by mangrove swamps. Coral reefs and seagrass
beds of T. testudinum and Syringodium filiforme are frequent. Seagrass beds of Thalassia here are in
depths from 20 em to 1.5 m.
Plants, water and sediment collections were made quarterly during the year. Immediately after
collection, plants and surficial sediment samples were frozen. Water samples were treated with concentrated nitric acid before freezing.
Mercury Determination.-Water
samples (100 ml) were taken in duplicate and the mercurial concentration was determined in a Perkin Elmer Atomic Absorption Spectrophotometer (Mod. 2380), by the
cold vapor method (Beaty, 1978).
Sediment Samples. A I-g aliquot from each sediment sample was taken in duplicate. Each aliquot was
708
BULLETIN OF MARINE SCIENCE, VOL. 56, NO.2, 1995
Table 1. Mercury concentration (ppb) in water, sediment, rhizome and leaf samples from Thalassia
testudinum located at Los Totumos Bay, Punta Moron, and Cayo Animas, Venezuela. Samples were
collected quarterly during a year. Results represent the mean of three samples, analyzed by duplicate.
Standard deviations in parentheses.
Mercury concentration (ppb)
Sampling month
Water
Sediment
Rhizome
Leaves
Los Totumos
February
May
August
November
I (0,9)
2 (I)
I (0,8)
1 (0.9)
7 (2)
6 (1)
9 (2)
6 (2)
15 (3)
9 (3)
9 (I)
8 (3)
6 (2)
6 (2)
4 (2)
5 (I)
Punta Moron
February
May
August
November
1 (0.9)
3 (I)
3 (2)
2 (I)
IS (4)
17 (3)
19 (6)
15 (6»
21 (3)
25 (6)
28 (5)
30 (7)
16 (6)
22 (5)
18 (4)
21 (4)
Cayo Animas
February
May
August
November
1(0.9)
1 (0.8)
2 (I)
2 (I)
26 (3)
29 (5)
32 (5)
37 (7)
41 (7)
37 (9)
39 (6)
43 (3)
30 (6)
24 (8)
19 (5)
25 (4)
digested for 4 h in a water bath at 60°C, after adding 3 ml of sulfuric acid and 3 ml of hydrogen
fluoride. Mercury concentration was determined by the cold vapor method (Beaty, 1978).
plants were separated into leaves and rhizomes,S g of each were digested
in a water bath at 60°C for 6 h after adding 3 m1of nitric acid and 5 ml of sulfuric acid. The mercurial
concentration in these samples was also determined by the same method (Beaty, 1978).
Plant Samples.-Thalassia
RESULTS
AND DISCUSSION
Mercurial levels found in the water, in three sampling stations, were between
1 and 2 ppb. In areas poorly or moderately contaminated by heavy metals, water
does not generally contain noticeable quantities of mercury, given that this metal,
once that it is present in the water in its ionic form, can constitute a wide variety
of complexes and chelates with organic compounds or attaches to the sediment
particles (Grant, 1973; Aubert et aI., 1973). Besides, microorganisms make inorganic mercury available for incorporation into trophic webs, by conversion to
monomethyl and dimethyl mercury. Since monomethyl mercury is not only the
most toxic form, but is also somewhat soluble and volatile, it can be rapidly
assimilated by living organisms, given its affinity to proteins and other molecules
that contain -SH groups (Barlett, 1979; Barlett et aI., 1978). Thus, mercury in the
marine environment is mostly distributed between sediments and biota (Forstner
and Wittmann, 1979).
Sampling made in Los Totumos Bay, a location supposedly free of mercurial
pollution, allowed us to reference mercury content in sediment and Thalassia
plants. Before the anthropogenic disturbances, the background mercury concentration in sedimentary material along the Venezuelan coast was not known. At
Los Totumos Bay, mercury levels found in Thalassia leaves were in a range of
3 to 6 ppb, in the rhizome concentrations were between 8 and 15 ppb (Table 1).
Mercury levels in sediment were between 6 and 9 ppb. These values were similar
or lower than the concentration of 10 ppb reported for sediment samples from
areas defined as non-polluted by this metal (Knauer, 1976). Values found in the
NOTES
709
rhizome of Thalassia in this locality were almost always higher than the values
found in the sediment.
Mercurial levels in sediments collected in Punta Moron (Table 1) and Cayo
Animas (Table 1) were comparable to the levels found in sediment of the Gulf
of Nicoya in Costa Rica (Dean et aI., 1986), the Florida river's mouth (Selli et
al., ] 973), and some zones of the Mediterranean Sea (Renzoni et aI., ]973; Baldi
et al., ] 979), all of them affected by industrial effluents. They were also comparable to the levels reported for the west coast of India (Zingdee and Desay,
]981; Sasamal et aI., 1987), affected by effluents from industries of caustic soda,
caustic potassium, chloride, plastics, paints, paper pulp, fungicides and other
chemicals.
Values found in sediments from Cayo Animas (Table 1) were always higher
than the values from Punta Moron (Table 1). At Cayo Animas, mercurial levels
were between 26 and 37 ppb, whereas in Punta Moron they were between 15 and
18 ppb. Results obtained in these two localities showed that mercury concentration in the rhizome of Thalassia was always higher in relation to the sediment.
Similarly, the mercurial concentrations in the rhizome were always higher as
compared to the leaves. Apparently, Thalassia testudinum accumulated this contaminant, especially in the rhizomes, at least for the mercury concentration found
in sediments during this study. It can be assumed that in a low or moderately
contaminated environment, the plant's rhizomes buried in the sediment concentrate the metal. This is in agreement with reports on Posidonia oceanica (Cristiani
et aI., 1980).
If, as follows from the results of this work, plants of T. testudinum have the
capability to accumulate mercury, they may be a potential mercury reservoir in
contaminated areas. This fact should be emphasized, given that seagrasses of
Thalassia support a great number of epiphytic organisms (Morgan and Kitting,
] 984), they also constitute a space for feeding and protection against predation
for many species (Pollard, 1984), they allow the settlement of many benthic organisms or infauna in the sediment (Orth, 1984), and playa remarkable role in
the cycling of several nutrients in coastal water (Short, 1987). The possible effects
of mercury on growth and development of T. testudinum plants should be studied.
LITERATURE CITED
Aubert, M., L. Pettit, B. Donnier and M. Barelli. 1973. Transfert de poilu ants metaliques au consommateur terrestre a partir du milieu marin. Rev. Inter. Oceanogr. Med. 30: 39-59.
Baldi, E, R. Bargagli and A. Renzoni. 1979. The distribution of mercury in the surficial sediments
on the northern Tyrrhenian Sea. Mar. Pollut. Bull. 10: 301-303.
Barlett, P. D. 1979. Studies on the distribution, mobility and methylation of mercury in the environment. Ph.D. Thesis, Leicester Polytechnic, Leicester. 127 p.
---,
P. J. Craig and S. E Morton. 1978. Total and methylmercury levels in British estuarine and
marine sediments. Sci. Total Envir. 10: 245-251.
Beaty, R. 1978. Concepts, instrumentation and techniques in atomic absorption spectrophotometry.
Perkin Elmer Corp., U.S.A. 49 pp.
Cristiani, G., R. Gassend and H. Augier. 1980. Etude de la contamination experimenta]e de ]a phanerogame marine Posidonia oceanica (L) Deli]e, par les composes mercuriques. Partie I: modalites
de la contamination par Ie chlorure de mercure. Env. Pollut. 23: ]53-162.
Dean, H. K., D. Maurer, J. A. Vargas and C. H. Tinsman. 1986. Trace meta] concentration in sediments
and invertebrates from the Gulf of Nicoya, Costa Rica. Mar. Pollut. Bu]l. 17: 128-131.
Forstner, U. and G. T. Wittmann. 1979. Meta] pollution in the aquatic environment. Springer-Verlag,
Berlin, Heidelberg, New York. 217 pp.
Grant, C. A. 1973. Pathology of experimental methyl mercury intoxication. In M. Miller and T.
Clarkson, eds. Mercury, mercurials and mercaptans. Springfield, Illinois. 318 pp.
Ig]esias, N. and P. Penchaszadeh. 1983. Mercury in sea stars from Golfo Triste, Venezuela. Mar.
Pollut. Bull. 14: 396-398.
710
BULLETIN
OFMARINE
SCIENCE,
VOL.56, NO.2, 1995
Ishizaki, Ch. and J, Urich. 1985. Mercury contamination of food: a Venezuelan case study, Interciencia 10: 173-178.
Knauer, O. A. 1976, Immediate industrial effect on sediment mercury concentrations in a clean coastal
environment. Mar. Pollut. Bull. 7: 112-115.
Monaco, M, and P. Ozaeta. 1979. Informe preliminar presentado a la Comisi6n Interministerial del
Ministerio del Ambiente y de los Recursos Naturales Renovables (MARNR ed,), 20 pp.
Morgan, M, D. and C. L. Kitting. 1984. Productivity and utilization on the seagrass Halodule wrightii
and its attached epiphytes. Limnol. Oceanogr. 29: 1066-1076.
Orth, R. J. 1984. The importance, of sediment stability in seagrass communities. Pages 281-300 in
Bruce C. Coull, ed. Ecology of marine benthos. University of South Carolina Press, Columbia,
Parra, G. 1974. Estudio integral de la cuenca del rfo Yaracuy. Direccion de Malario-Iogfa y Saneamiento Ambiental. Ministerio de Sanidad y Asistencia Social (MSAS ed.). 341 pp.
Pollard, D. A. 1984. A review of eco]ogical studies on seagrass-fish communities, with particular
reference to recent :;tudies in Australia. Aquatic Bot. 18: 3-42.
Renzoni, A., E. Bacci and L. Falciai. 1973. Mercury concentrations in the water, sediments and fauna
of an area of Tyrrhenian coast Rev, Inter. Oceanogr. Med. 31/32: 17-45.
Sasarna], S. K., B. K. Sahu and R. C. Panigrahy. 1987. Heavy metals in coastal sediments from India.
Mar. Pollut. Bull. 18: 132-136.
Selli, R., M. Frignani, C. M. Rossi and R. Viviani. 1973. Mercury content in the sediments of the
Adriatic and the Tyrrhenian. Bull. Geol. Soc, Greece 10: 177-179,
Short, F. T. 1987. Effcct of sediments nutrients on seagrasses: literature review and mesocosm experiment. Aquatic Bot. 27: 41-57.
Urich, J. 1981. Estudio comparativo de los niveles de mercurio total en la ictiofauna de Golfo Triste
(Edo. Carabobo) y zona orienta] de ]a costa de Venezuela. M.Sc. Thesis, Inst. Venez. Invest.
Cient., Venezuela, ] 15 pp.
Zingdee, M. D. and B. N, Desay. 1981. Mercury in Thana Creek Bombay Harbour. Mar. Pollut, Bull,
]2: 237-241.
DATEACCEPTED:June I, 1994.
ADDRESS: Instituto de Tecnologia y Ciencias Marinas (INTECMAR), Universidad Simon Bolivar,
Apartado postal 89000, Caracas l080-A, Venezuela.
BULLETIN
OFMARINE
SCIENCE,
56(2):
710-717, 1995
ETHNOICHTHYOLOGY OF SOUTHERN COASTAL FISHERMEN:
CASES FROM BUZIOS ISLAND AND
SEPETIBA BAY (BRAZIL)
A. Begossi and J. L. de Figueiredo
Ethnobiology deals with the perceptions, uses, and classifications man has for
the biotic environment. It includes the study of the types and uses of resources,
of their names, and of the logic behind their classification. Populations living
close to natural resources have, in general, a deep knowledge of those resources,
useful for food, trade, medicine and ritual practices. There is a vast literature on
ethnobiology, such as on ethnobotany (Prance et aI., 1987), ethnornithology (Boster et aI., 1986), ethnoentomology (Posey, 1981) and ethnoichthyology (Begossi
and Garavello, 1990; Marques, 1991; Morril, 1967).
Studies on ethnobiology have contributed to advances in biological knowledge,
through the finding of new species (Posey, 1986) and through new data on fish
behavior (Marques, 1991), The implication folk knowledge has on the conservation of biodiversity is indisputable: it is essential to do inventories of tropical
fauna and to know more about species, Traditional seafolk have a fundamental