Copepod Community Research Articles

Production of tropical copepods in Kingston Harbour, Jamaica: the importance of small species

The copepod community observed during an 18-month period at the mouth of eutrophic Kingston Harbour, Jamaica, was dominated by small species of Parvocalanus, Temora, Oithona, and Corycaeus. Mean copepod biomass was 22.1 mg AFDW m−3 (331 mg m−2). Annual production was 1679 kJ m−2, partitioned as 174 kJ m−2 naupliar, 936 kJ m−2 copepodite, 475 kJ m−2 egg and 93 kJ m−2 exuvial production. All nauplii, most copepodites and many adults, equivalent to half of the biomass and production, were missed by a standard 200-μm plankton net, emphasizing the importance of nauplii and small species in secondary production estimates. The evidence suggests that growth rates and production are generally not food limited, and we speculate that size-selective predation shapes the structure of the harbour community. Biomass and production are higher than previous estimates for tropical coastal waters, but comparable to other eutrophic tropical embayments and many productive temperate ecosystems. Far from being regions of low productivity, tropical zooplankton communities may have significant production and deserve greater research attention than they currently receive.

Copepod Assemblages in Surface Waters of the Western Gulf of Mexico

Composition, distribution, and abundance of the pelagic copepods collected in surface waters of the western Gulf of Mexico during the EMOAPI cruise (May, 1993), were determined. A total of 55 species were identified. The most abundant were Temora turbinata, Clausocalanus furcatus, Paracalanus aculeatus, and Corycaeus speciosus; together they constituted more than 50% of the copepods in numbers. From cluster analysis (Bray-Curtis Index) using the 12 most abundant copepod species, four faunistic assemblages were recognized. Their arrangement in the surveyed area followed the conditions of the coastal-oceanic gradient. Resulting assemblages were compared with previous surveys and constitute a detailed description of faunal variations of the copepod community in the area. The structure of the local copepod community was related to the prevailing hydrographic conditions dominated by heavy land effluents and by the intrusion of an oceanic front into the shelf area mainly related to the presence of an eddy derived from the Loop Current. Differences in copepod community structure seem to be related mainly to variations within the coastal-oceanic gradient.

Copepod Assemblages From a Reef-Related Environment in the Mexican Caribbean Sea

Results on copepod composition and abundance from samples obtained in a reef zone in the northern part of the Mexican Caribbean Sea are presented here. Samples were collected monthly from June to December 1991 at four stations, two of them in the reef lagoon and two at the fore-reef. Salinity and temperature were homogeneous at the four sampling sites. Copepods in the lagoon showed a higher abundance, lower species richness and a clear dominance of Acartia spinata. Copepods outside the lagoon were less abundant, but with a larger number of species. Acartia spinata and Farranula gracilis were the most conspicuous species, the former being the dominant form of the reef lagoon community and the latter so at the adjacent sea stations. The local distribution of Undinula vulgaris seems to be related to the extent of oceanic influence throughout the coastal-oceanic gradient. The reef-associated copepod community shows a strong neritic-oceanic affinity, which is related to the narrowness of the shelf, the local hydrodynamics, and the wind regime. The Bray-Curtis Index clustered the stations with similar features in several different ways during the survey. Despite these month-to-month differences, the general behaviour of the local copepod community seems to be quite homogeneous when compared with other reef systems. This effect could be related to the circulation pattern in the area, which favours a continuous, strong oceanic influence along the reef.

Copepod egg production rates in the Pomeranian Bay (Southern Baltic Sea) as a function of phytoplankton abundance and taxonomic composition

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 174:183-195 (1998) - doi:10.3354/meps174183 Copepod egg production rates in the Pomeranian Bay (Southern Baltic Sea) as a function of phytoplankton abundance and taxonomic composition Katrin Schmidt*, Paul Kähler, Bodo von Bodungen Institut für Ostseeforschung an der Universität Rostock, Seestraße 15, D-18119 Rostock, Germany *E-mail: katrin.schmidt@io-warnemuende.de ABSTRACT: The copepod community of the Pomeranian Bay, in the outer part of the Oder Estuary (Southern Baltic Sea), is dominated by Acartia bifilosa Giesbrecht in winter and spring and by A. tonsa Dana in autumn. During summer both species co-occur. The egg production of these species was studied in 1994/1995. Rates (eggs female-1 d-1) were found to vary both seasonally and spatially. In winter, egg production rates of A. bifilosa were low, but showed a positive response to increasing chlorophyll a concentrations. During the late phase of the spring bloom (dominated by the diatom Skeletonema costatum), egg production of A. bifilosa was clearly higher than in winter, while water temperature remained at a low level. Phytoplankton concentrations during the spring bloom varied, but egg production rates were uniform all over the bay, suggesting production was not food limited. Length-specific weight and lipid content indicate that females were in good physiological condition. During summer and autumn, both high and very low egg production rates were observed for both species. The relation between egg production rate and chlorophyll a concentration was negative. The analysis of the phytoplankton composition in summer suggested that a high proportion of dinoflagellates was beneficial for egg production whereas high proportions of cyanobacterial colonies and filaments had negative effects. Except during the spring bloom period, the egg production of Acartia spp. in the Pomeranian Bay was limited by the amount and quality of phytoplankton. KEY WORDS: Acartia spp. · Egg production · Phytoplankton · Food quality · Pomeranian Bay Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 174. Publication date: November 26, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.

Importance of microzooplanktonic crustaceans in the coastal food chain: Bay of Marennes-Oléron, France

Modelling biological processes in marine ecosystems requires a good knowledge of the relationships between the different compartments of the ecosystems. Microzooplanktonic crustaceans are often neglected in field feeding studies, due to the difficulties in identification and to their small size. In coastal areas, difficulties are enhanced by the great quantities of particulate organic matter in the water column. Euterpina acutifrons is the major component of the zooplankton community in the Bay of Marennes-Oléron (south-west France) during the algal spring bloom (nauplii strongly dominate the copepod community). The grazing impact of the copepod Euterpina acutifrons (microzooplanktonic and mesozooplanktonic fractions) on the algal standing stock was estimated in the Marennes-Oléron Bay during this period by means of both laboratory experiments and field data. The results suggest that grazing pressure of the microzooplanktonic stages was similar to the pressure exerted by the mesozooplanktonic ones, underlining the significant role of small copepod stages in marine systems in terms of grazing impact. Our results indicate that the daily grazing pressure exerted by the whole population is quite low in the Marennes-Oléron Bay (about 15 % of the algal standing stock).

Seasonal variations in biomass, growth rate and production rate of the small cyclopoid copepod Oithona davisae in a temperate eutrophic inlet

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 163:37-44 (1998) - doi:10.3354/meps163037 Seasonal variations in biomass, growth rate and production rate of the small cyclopoid copepod Oithona davisae in a temperate eutrophic inlet Shin-ichi Uye*, Kazuhiro Sano Faculty of Applied Biological Science, Hiroshima University, 4-4 Kagamiyama 1 Chome, Higashi-Hiroshima 739-8528, Japan *E-mail: suye@ipc.hiroshima-u.ac.jp We investigated the seasonal variations in biomass, somatic growth rate and production rate of the small cyclopoid copepod Oithona davisae in Fukuyama Harbor, a eutrophic inlet of the Inland Sea of Japan. The carbon biomass of the population, excluding nauplii, was lowest in early spring and increased exponentially in early summer to a maximum of 92.2 mg m-3 in mid-June. Thereafter, it was relatively high, except for a mid-summer decline, until fall. The specific growth rates of naupliar and copepodite stages were estimated from their body weight increments and stage durations, assuming that in this highly eutrophic inlet growth is food-satiated for this species. They increased exponentially with increasing temperature, ranging from 0.088 to 0.357 d-1 for nauplii and from 0.060 to 0.446 d-1 for copepodites within the annual temperature range of 8.9 to 28.2°C. The production rate as a sum of somatic growth rate of copepodites and egg production rate of adult females varied similarly to, but showed a wider range than, the biomass variation. Annual integrated carbon production was 650 mg m-3 yr-1, or 4.88 g m-2 yr-1, 94% of which was attained between June and October. Of the production, copepodite somatic growth and female egg production comprised 75 and 25%, respectively. O. davisae contributed 26% of the annual copepod community production in Fukuyama Harbor. Biomass · Growth · Production · Cyclopoid · Oithona · Inland Sea of Japan Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 163. Publication date: March 12, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.

Copepod grazing in the equatorial Pacific

The vertical distribution of copepod (>64 µm) grazing was measured on the equator at 140°W during March/April (19 d) and October 1992 (21 d). El Niño conditions prevailed during the March/April time series. Hydrographic variables were similar to the climatological mean during the October time series. We found higher weight‐specific copepod filtration rates in October when mixed‐layer temperatures were generally 3°C cooler; there were more phytoplankton >2.0 µm and more calanoid copepods than in March/April. The grazing impact of the copepod community (biomass × weight‐specific filtration rate) was similar for the 64–200‐µm copepod fraction during both time series (0.023 and 0.028 d−1 for March/April and October) but was higher in October (0.114 d−1) as compared to March/April (0.040 d−1) for >200‐µm copepods. Within‐cruise variability was highest in October when a tropical instability wave advected colder water with higher nitrate and chlorophyll through the study area. We observed over six‐fold increases in copepod biomass, weight‐specific filtration rates, and copepod grazing rates during this advective event. Grazing rates calculated by assuming that copepods capture only >2‐µm phytoplankton (0.25 d−1 in March/April; 0.88 d−1 in October) suggest that copepod grazing could limit the production of >2‐µm phytoplankton, primarily diatoms, in October but not during the El Niño conditions of March/April when there was less copepod biomass as well as a greater dominance of cyclopoid copepods. Estimates of fecal pellet production compared with export flux measurements suggest that most copepod fecal pellets produced in the euphotic zone decompose or are ingested by other zooplankton. Our estimates of copepod grazing rates on phytoplankton and protozoa are in agreement with previous calculations, which suggest that most of the carbon consumed by copepods in the equatorial Pacific is from protozoa.

Mesozooplankton of Shelikof Strait, Alaska: abundance and community composition

Zooplankton was sampled in Shelikof Strait and some of the surrounding shelf waters from March to October 1985, and then in Shelikof Strait during spring 1986–1989, using 150 and 333 μm mesh nets. The median integrated abundance of copepods in spring was 1–2 orders of magnitude greater in the Strait (maximum depth >250 m) than over shallower, adjacent regions of continental shelf. Zooplankton fauna was a mixture of oceanic and continental shelf taxa, and among the copepods was strongly influenced by abundance of two deep-water species, Neocalanus plumchrus and Metridia pacifica Seasonal development of the copepod community in Shelikof Strait followed similar patterns over the 5-year period. Biomass of copepods showed some large interannual differences related mostly to abundance of the oceanic taxa. Large interannual differences were found for some of the other zooplanktonic taxa as well, but there did not appear to be any correspondence between the patterns shown by these groups and those shown by the copepods. Although euphausiids were not quantitatively sampled, the taxonomic composition and relative abundance and seasonality of species within this group are reported.

Spatio-temporal patterns in the copepod community in Malangen, Northern Norway

Spatio-temporal patterns in the copepod community in Malangen, Northern Norway

Copepod Community Structure at Bahia Magdalena, Mexico during El Niño 1983–84

Changes in the community structure and distribution patterns of 71 species of copepods collected during eight oceanographic surveys at Bahia Magdalena, Mexico were analysed. From March 1983 to January 1985, the responses of the copepod community structure to the seasonal environmental conditions and temporal changes during the peak warming of the El Niño event 1982–83, the relaxation phase in 1984, and the winter 1984–85 cooler period were studied. As in other estuaries and bays, the copepod community had a few dominant species, which have a seasonal succession throughout the year related to seasonal changes in sea-surface temperature. There are two major successional stages in the annual cycle of zooplankton development. During the warming period (July–October of 1983 and 1984), Acartia lilljeborgiiGiesbrecht and Acartia tonsaDana (tropical affinity) were the dominant species in the copepod community. During the cooler period (December–June), the dominant species was Paracalanus parvus(Claus). During Summer and Autumn 1983 (El Niño peak), an unusual increase of tropical-equatorial copepod species were found, that are regularly found offshore. The resident species Acartia clausiGiesbrecht was replaced by A. tonsa. Despite these changes in the species composition because of El Niño, seasonal succession is the general rule in Bahia Magdalena and was only enhanced by the presence of several tropical species during the warmest period.

Large-scale patterns of diel vertical migration in the North Atlantic

Samples historically collected and analysed by the Continuous Plankton Recorder (CPR) survey in the North Atlantic were used to examine large-scale spatial patterns in both the normal diel vertical migration (normal DVM) behaviour and the mean body size within epi-pelagic copepod communities. Normal DVM was most marked in the northwest Atlantic and less marked in the northeast Atlantic and in shallow coastal areas such as around the U.K. and on the Grand Banks of Newfoundland. These patterns of normal DVM were strongly correlated with patterns of mean body size, with normal DVM being more marked in those areas where larger species predominated. In both the northwest and northeast Atlantic, marked seasonal changes occurred in the migrating biomass. In the northwest Atlantic, Euchaeta norvegica and Calanus finmarchicus were the most important contributors to the total migrating biomass, while in the northeast Atlantic the most important contributors were E. norvegica, Metridia lucens and Pleuromamma robusta.

Copepod communities in lakes of varying trophic degree

Copepod communities in the pelagic of 22 lakes of varying trophic degree were studied during the summer months of the years 1989 to 1991. In total 6 species were monitored, one calanoid copepod (Eudiaptomus gracilis), and 5 species of cyclopoid copepods (Acanthocyclops robustus, Cyclops abyssorum, Cyclops vicinus, Mesocyclops leuckarti, Thermocyclops crassus). The calanoid copepod predominated in the oligo-mesotrophic lakes. Among cyclopoid copepods M. leuckarti and Cyclops abyssorum preferred oligo-mesotrophic conditions while the other species predominated in the eutrophic lakes. C. vicinus, generally regarded as a winter species which should undergo a diapause during summer, formed summer generations in the eutrophic lakes. This particular deviation from the normal life cycle is interpreted as a strategy to optimize the reproductive output. It implies that even during summer when competition with cladocerans is intense eutrophic conditions can provide sufficient food for the development of the nauplii and for the reproduction of the adults. Calculation of the association coefficients revealed that among cyclopoid copepods generally a large species (C. vicinus) and a small species (T. crassus or M. leuckarti) co-exist. However, frequent associations of M. leuckarti and T. crassus suggest that these species use different food sources. The decline of the calanoid copepod in the eutrophic lakes is probably a result of a higher predation pressure on this group; possibly cyclopoid copepods benefit from their distinct mating behaviours.

Influence of polycyclic aromatic hydrocarbons on the meiobenthic-copepod community of a Louisiana salt marsh

The influence of sediment contaminated with polycyclic aromatic hydrocarbons (PAHs) on the meiobenthic copepod community of a Louisiana salt marsh was examined with microcosms of sediment containing natural faunal assemblages. Microcosms were dosed with PAH-contaminated sediment that ranged in concentration from 0.3 (controls) to 27 mg PAH/kg dry sediment, and effects were followed for 28 days. Data suggest that highest doses (High-PAH) elicited avoidance behavior by Pseudostenhelia wellsi (Coull and Fleeger) copepods and nauplii, particularly 12 h after contaminants were added (Day 0). Weaker avoidance behavior was indicated in non- P. wellsi species that was manifested as increases in nauplius copepod ratios. Nematode copepod ratios were calculated for each of 4 species ( P. wellsi, Coullana sp., Enhydrosoma sp., and Onychoeamptus mohammed (Blanchard and Richard)); only nematode/ P. wellsi ratios were significantly affected by PAH. High-PAH treatments also lead to a higher proportion of females in P. wellsi and Coullana sp. This effect was only observed from Day 7 on and is interpreted as an indication of disproportionately high mortality of males. Collectively, our data demonstrate that relatively low-level PAH contamination may cause many ecologically important impacts on copepod community structure that may not be detected at the level of higher taxon.

Subantarctic copepods in an oceanic, low chlorophyll environment:ciliate predation, food selectivity and impact on prey populations

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 130:85-96 (1996) - doi:10.3354/meps130085 Subantarctic copepods in an oceanic, low chlorophyll environment: ciliate predation, food selectivity and impact on prey populations Atkinson A Copepod feeding rates and food selectivity were measured at an oceanic subantarctic site over 5 d in February 1994. A series of gut fluorescence and gut evacuation experiments was carried out for species ranging in size from Oithona similis to Pleuromamma robusta. The copepods were also incubated in ambient seawater to compare their clearance rates on ciliates, diatoms and total chlorophyll a (chl a), using microscope counts and chlorophyll budgets. Mesozooplankton were concentrated into the top 50 m layer where biomass was high (5.5 g dry mass m-2) and comprised mainly (65%) of copepods. Copepod biomass was dominated by copepodite CV of Calanus simillimus. Numerically, however, Oithona spp. (mainly O. similis) constituted 85% of the copepods. These 2 species dominated copepod grazing and contributed to community grazing in about equal proportions. Chl a concentrations were low (~0.7 mg m-3) and were comprised of mostly nano- and picoplankton. Low daily phytoplankton carbon rations were derived from the 2 methods which measured total chl a consumption. These ranged from 1.5% (female CVI C. simillimus) to 34% of body carbon (late stage copepodites of Oithona spp.). These values were generally well below their estimated respiratory requirements, and probably reflected phytoplankton shortage because clearance rates were fairly high. Clearance rates for total chl a in the incubations tended to be less than those for the counted taxa &GT10 um, suggesting that some of the chl a was in cells too small to be eaten. Feeding selectivity followed a similar pattern across the 4 incubations. Highest clearance rates were on ciliates (~15 um), dinoflagellates (~20 um) or the diatom Corethron sp. (~200 um). Ciliates and dinoflagellates were cleared faster than centric diatoms of similar overall dimensions. It is suggested that the copepods were preying on protozoans preferentially, in response to phytoplankton shortage. Allometric relationships were used to derive the grazing and predation impact of the whole copepod community on primary production and estimated ciliate production. Less than 4% of primary production was removed per day. Copepod predation on ciliates was higher: 57% of daily production, assuming a net growth rate for ciliates of 0.1 d-1. Subantarctic . Copepods . Selective feeding . Ciliates . Allometry Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 130. Publication date: January 11, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.

Planktonic Copepods of Bahia De La Ascensión, Caribbean Coast of Mexico: a Seasonal Survey

AbstractThe composition, abundance, and distribution of planktonic copepods collected at Bahia de la Ascensión, on the east coast of the Yucatan Peninsula, were analyzed during all three climatic periods of a year cycle (August, 1990-July, 1991). Highest mean copepod abundance was observed during the "nortes" period (524 org. 100 m-3), lowest values occurred during the dry season (91 org. 100 m-3). A total of 35 copepod species were identified, the most abundant were Acartia lilljeborgii, A. spinata, Labidocera scotti and L. mirabilis. Salinity gradients were weak and were not considered a relevant factor of the local copepod distribution. Spatial distribution of copepod densities throughout the year seemed to be related to different climatic regimes. From cluster analysis (Canberra Index), three facies could be identified: a bay facies, a neritic facies, and a mixed or semi-neritic facies. Copepod distribution during the three seasons was variable and showed the seasonal intensity of the marine influence in the system and the effect of the winds regime in the local copepod community.

Annual biomass and production of the oceanic copepod community off Discovery Bay, Jamaica

Monthly samples were collected in oceanic waters off Discovery Bay, Jamaica, in 60- and 200-m vertical hauls, using 200- and 64-μm mesh plankton nets, from June 1989 to July 1991. Length-weight regressions were derived for twelve genera of copepods (R2=0.79 to 0.97). For eight occasions spanning the study period, biomass estimates generated from these length-weight regressions differed by only 3% from direct weight determinations. The mean ash content of copepods was 7.1%, and the energy density was 20.8 kJ g-1 ash-free dry weight (AFDW). Mean annual biomass of the total copepod community in the upper 60 m was 1.83 mg AFDW m-3 (range 1.14 to 2.89 mg AFDW m-3), and for the 200-m water column was 0.96 mg AFDW m-3 (range 0.12 to 1.99 mg AFDW m-3). Estimates of generation times for five common taxa ranged from 16.1 to 33.4 d. None of the taxa investigated displayed isochronal development; in general, stage duration increased in later copepodite stages. Weight increments showed a significant decrease in later copepodite stages, but with strong reversal of the trend from stage 5 to adult female in most species. Daily specific growth rates also declined in later copepodite stages, and ranged from 1.49 d-1 in stage 1–2 Paracalanus/Clausocalanus spp. to 0.04 in stage 5-female of Oithona plumifera. Progressive food limitation of somatic copepodite growth and egg production is postulated. Naupliar production was 50.4 to 59.5% of copepodite production, and egg production was 35.1 to 27.7% of copepodite production in the 60-and 200-m water columns, respectively. Total annual copepod production, including copepodites, nauplii, eggs and exuviae, was 160 kJ m-2 yr-1 for the upper 60 m and 304 kJ m-2 yr-1 for the upper 200 m. Secondary production of the copepod community in oceanic waters off Discovery Bay approaches 50% of the corresponding value in tropical neritic waters.

Annual structure of the copepod community and its associated pelagic environment off Discovery Bay, Jamaica

Monthly samples were collected in oceanic waters off Discovery Bay, Jamaica, in 60- and 200-m vertical hauls, using 200- and 64-μm mesh plankton nets, from June 1989 to July 1991. Sixty-nine species of copepods were identified: nauplii, copepodites and adults were separately enumerated. Total copepod abundances (all stages) ranged from 695 to 4120 m-3 in the upper 60 m, and from 483 to 3319 m-3 in the 200-m water column, without any clear seasonal pattern. With the exception of temperature, no seasonal variations in physico-chemical (chlorophyll a, S‰, particulate organic carbon, particulate protein) or biological variables were evident. Nauplii, adults and copepodites of selected taxa, and two chaetognath species, showed no significant variations in body length. Significant variantions in reproductive index were detected for several species, but without seasonal trends; many species appear to be continuous or intermittent breeders. There was no evidence of seasonal pattern in overall community composition or diversity, or evidence of changes due to water mass advection. The copepod community can be divided into a recurrent group of 13 (at 60 m) to 17 (at 200 m) “perennial” species, present year-round, and associated “ephemeral” groups of 1 to 3 species, present randomly for 1 to 4 consecutive months. The most plausible explanation of these patterns is that broad areas of the Caribbean Sea are dominated by the community of perennial species, while the ephemeral species represent the superimposed influence of local mesoscale gyres.

Meiobenthic distribution and nematode community structure in five European estuaries

Meiofauna from the intertidal zone of five European estuaries (Ems, Westerschelde, Somme, Gironde, Tagus) was investigated. Samples represented a cross section of various benthic habitats from near-freshwater to marine, from pure silts to fine-sandy bottoms. The meiobenthic community comprised everywhere a fauna strongly dominated by nematodes, with meiobenthic density increasing with increasing salinity. The Ems differed from the other estuaries due to the presence of a well developed community of Copepods, Gastrotrichs, large Ciliates and/or soft-shelled Foraminiferans in some sites. The Westerschelde stood out due to the near-absence of harpacticoid copepods and, as in the Tagus, the lower meiobenthic densities in the marine part of the estuary. For nematode community analysis, we also included data from the Tamar which were obtained from the literature (Warwick & Gee, 1984). This resulted in the enumeration of 220 species, belonging to 102 genera, each with a characteristic distribution along the salinity, sedimentary and latitudinal gradients. Using the multivariate technique CANOCO, a zonation along these different physicochemical determinants was observed as well although salinity and sediment characteristic (scale of hundreds of meters to kilometers) proved to be more important in explaining community structure than latitudinal differences (scale of hundreds of kilometers). Nematode diversity was nearly entirely determined on the genus level and was positively related to salinity. Deviations from this general trend in the Gironde and the Tamar were attributed to sedimentary characteristics or to low macrobenthic predation. The presence of a typical opportunistic colonizing nematode species Pareurodiplogaster pararmatus in the low-salinity region of the Gironde could indicate (organic?) pollution or disturbance of the intertidal mud-flats.

Secondary production of the brackish copepod communities and their contribution to the carbon fluxes in the Westerschelde estuary (The Netherlands)

The zooplankton community of the brackish part of the Westerschelde estuary (November 1989–October 1990) was dominated by two calanoid copepods, Eurytemora affinis and Acartia tonsa. Eurytemora was present during a longer period of the year and was much more important in terms of total abundances and biomasses than Acartia.

Eleven years of time-series analysis on the net-zooplankton community in the Gulf of Trieste

Net-zooplankton data collected monthly at one coastal station of the Gulf of Trieste (Northern Adriatic Sea) from 1970 to 1980 were analysed in order to test the existence of any successional trend among the copepod community. No periodicity was evident for single species. However, a clear periodicity was found for two species groups obtained by cluster analysis. One group was characterized by Acartia clausi and Temora longicornis and showed a regular appearance in late spring–summer. The other group was characterized by Temora stylifera and Oncaea sp. and showed a regular appearance in autumn–winter. Time-series analysis of the diversity of the copepod community showed a clear 12-month periodicity with winter maxima corresponding to the highest level of stability. However, a decreasing trend of the copepod biomass appears to have originated in the mid-1970s. The biomass decrease was probably caused by Noctiluca miliaris and Pelagia noctiluca blooms.