Mesozooplankton beneath the summer sea ice in McMurdo Sound,Antarctica: abundance,species composition,and DMSP content

The summer Phaeocystis antarctica bloom increases under-ice phytoplankton biomass in McMurdo Sound, Antarctica. The magnitude of mesozooplankton grazing on this bloom is unknown, and determines whether this production is available to the pelagic food web. We measured mesozooplankton abundance and body content of dimethylsulfoniopropionate (DMSP) during the McMurdo Sound austral summer (2006 and 2006–2007). Abundance varied from 20 to 4,500 ind. m⁻³ (biomass 0.02–274.0 mg C m⁻³), with peaks in mid-December and late-January/February. Abundance was higher but total zooplankton biomass lower in our study compared to previous reports. Copepods and the pteropod Limacina helicina dominated the zooplankton in both abundance and biomass. DMSP was detected in all zooplankton groups, with highest concentrations in copepod nauplii and L. helicina (95 and 54 nmol mg⁻¹ body C, respectively). Experiments suggested that L. helicina obtains DMSP by directly grazing on P. antarctica, which often accumulates to high biomass under the summer sea ice in McMurdo Sound.     

Mesozooplankton structure in Dolgaya Bay (Barents Sea)

The community structure of mesozooplankton was investigated in Dolgaya Bay (southern Barents Sea), a subarctic fjord, using a Juday net (0.168-mm mesh size) in July, 2008. A total of 39 species and higher taxa were found. Average abundance, biomass and diversity (±standard error) were 153,403 ± 15,855 ind m⁻², 570 ± 61 mg dry mass m⁻², and 2.25 ± 0.09, respectively. Copepods were the most numerous species. The mesozooplankton communities were dominated by omnivores (Oithona similis and Acartia spp.). Vertical distribution of the mesozooplankton was characterized by copepod dominance at each sampled layer. There were no significant correlations among physical variables and biological parameters, except negative correlation for the mean biomass and mean water temperature.     

Copepod community structure and abundance in a tropical mangrove estuary,with comparisons to coastal waters

Zooplankton, sampled at five stations from the upper Sangga estuary (7 km upstream) in Matang Mangrove Forest Reserve (MMFR), Malaysia, to 16 km offshore, comprised more than 47% copepod. Copepod abundance was highest at nearshore waters (20,311 ind m⁻³), but decreased toward both upstream (15,572 ind m⁻³) and offshore waters (12,330 ind m⁻³). Copepod abundance was also higher during the wetter NE monsoon period as compared to the drier SW monsoon period, but vice versa for copepod species diversity. Redundancy analysis (RDA) shows that copepod community structure in the upper estuary, nearshore and offshore waters differed, being influenced by spatial and seasonal variations in environmental conditions. The copepods could generally be grouped into estuarine species (dominantly Acartia spinicauda Mori, Acartia sp1, Oithona aruensis Früchtl, and Oithona dissimilis Lindberg), stenohaline species (Acartia erythraea Giesbrecht, Acrocalanus gibber Giesbrecht, Paracalanus aculateus Giesbrecht, and Corycaeus andrewsi Farran) and euryhaline species (Parvocalanus crassirostris Dahl, Oithona simplex Farran, and Bestiolina similis (Sewell)). Shifts in copepod community structure due to monsoonal effects on water parameters occurred at the lower estuary. Copepod peak abundance in mangrove waters could be associated with the peak chlorophyll a concentration prior to it. Evidence of copepod consumption by many species of young fish and shrimp larvae in the MMFR estuary implies the considerable impact of phytoplankton and microphytobenthos on mangrove trophodynamics.     

Mesozooplankton community in the Bay of Bengal (India): spatial variability during the summer monsoon

This study addresses the spatial variability in mesozooplankton biomass and composition in the Central and Western Bay of Bengal (India) during the summer monsoon season of 2001. Perennially warmer sea surface temperatures (>28°C), stratified top layer (sea surface salinity, 28–33 psu), high turbidity, and low nutrient concentrations due to weak/null upwelling and light limitation make the Bay of Bengal a region of low primary productivity. Despite this, mesozooplankton biomass values, i.e. 2.9–104 mg C m⁻³ in the Central Bay and 1.3–31 mg C m⁻³ in the Western Bay, observed in the mixed layer (2–51 m) during the summer monsoon were in the same range as reported from the more productive Arabian Sea. Mesozooplankton biomass was five times and density 18 times greater at stations with signatures of cold-core eddies, causing a higher spatial heterogeneity in zooplankton distribution. Among the 27 taxonomic groups recorded during the season, Copepoda was the most abundant group in all samples followed by Chaetognatha. The dominant order of Copepoda, Calanoida, was represented by 132 species in a total of 163 species recorded. Oncaea venusta was the key copepod species in the Bay. In the Central Bay, the predominant copepod species were carnivorous/omnivorous vis-a-vis mostly herbivores in the Western Bay. Pleuromamma indica increased to its maximum abundance at 18°N in the Central Bay, coinciding with the lowest dissolved oxygen concentrations. The Central Bay had higher mesozooplankton biomass, copepod species richness and diversity than in the Western Bay. Although zooplankton biomass and densities were greater at the eddy stations, correlation between zooplankton and chl a was not statistically significant. It appears that the grazer mesozooplankton rapidly utilize the enhanced phytoplankton production in cold-core eddies.     

An approach for the assessment of risk from chronic radiation to populations of phytoplankton and zooplankton

A conceptual model of the effects of chronic radiation on a population of phytoplankton and zooplankton in an oceanic nutrient layer is presented. The model shows that there are distinct threshold dose rates at which the different plankton populations become unsustainable. These are 10,400 μGy h⁻¹ for phytoplankton and 125 μGy h⁻¹ for zooplankton. Both these values are considerably greater than the current screening values for protection of 10 μGy h⁻¹. The model highlights the effects of predator–prey dynamics in predicting that when the zooplankton is affected by the radiation dose, the phytoplankton population can increase. In addition, the model was altered to replicate the dose rates to the plankton of a previous ERICA Irish Sea assessment (24 μGy h⁻¹ for zooplankton and 430 μGy h⁻¹ to phytoplankton). The results showed only a 10% decrease in the zooplankton population and a 15% increase in the phytoplankton population. Therefore, at this level of dose, the model predicts that although the dose rate exceeds the guideline value, populations are not significantly affected. This result highlights the limitations of a single screening value for different groups of organisms.     

Basin scale distribution of zooplankton in the Ligurian Sea (north-western Mediterranean) in late autumn

Mesozooplankton biomass and abundance were evaluated in epipelagic waters at 59 stations covering the Italian sector of the Ligurian Sea (north-western Mediterranean) in December 1990. This region is characterised by a cyclonic circulation which encloses a central divergence zone and is associated with a main thermohaline front offshore the western Ligurian coast. At the end of autumn, mesozooplankton biomass (range: 0.80–4.24 mg DW m⁻³) and the abundance (range: 83.8–932 ind. m⁻³) were lower in the divergence zone. On the contrary, in the Ligurian frontal zone at the periphery of the divergence and on the eastern continental shelf the greatest values of biomass and abundance were recorded. Copepods and appendicularians dominated the mesozooplankton community, the main taxa being the copepods Clausocalanus spp. (46% of total zooplankton) and Oithona spp. (15%) and the appendicularian Fritillaria spp. (12%). Three hydrological sub-regions, i.e. the divergence, the eastern continental shelf and the periphery of the divergence, were characterised by different zooplankton communities and characteristic species. Environmental differences between the three zones were mainly related to changes in bottom topography, sea surface temperatures and quantity of particulate organic matter. Vertical mesozooplankton abundance and taxa distribution from the surface to 1,900 m depth were also examined in one station. The results showed that the bulk of the community was concentrated in the upper 200 m, small copepods being dominant particularly in the upper 50 m. The copepod community was more diversified in sub-superficial waters, with a maximum observed in the 200–400 m layer. The distributions of main zooplankton taxa described in epipelagic waters in the eastern Ligurian Sea in autumn were compared with their distribution at surface in the north-western Mediterranean obtained by sampling performed with the Continuous Plankton Recorder in 1997–1999. The analysis of the zooplankton community in CPR samples confirms the dominance of small copepods (Paracalanus spp., Clausocalanus spp., Oithona spp.) and appendicularians in the north-western Mediterranean in late autumn-winter and shows that their distribution is mainly related to the main mesoscale hydrographic features characterising this basin. Guest editors: S. Souissi & G. A. Boxshall Copepoda in the Mediterranean: Papers from the 9th International Conference on Copepoda, Hammamet, Tunisia     

Zooplankton of two arms in the Morava River floodplain in Slovakia

The species composition, seasonal dynamic of biomass and density of zooplankton were studied in two arms with a different hydrological regime. The samples were collected in two hydrologically different years — extremely wet in 2002 and extremely dry in 2003. In the first arm the mean annual chlorophyll-a concentration was 31.6 μg L⁻¹ (2002) and relatively high 64.7 μg L⁻¹ during 2003. Mean seasonal zooplankton wet biomass was low and varied: 11.6 g m⁻³ (2002) and 2.93 g m⁻³ (2003). Total zooplankton density was high (7,370 N L⁻¹) in 2002, when rotifers predominated in an open water zone and contributed up to 81% of the total zooplankton biomass and 83% of the total zooplankton density. In medial and littoral zone, in total, 22 cladoceran and 15 copepod species were identified. In the second arm the mean annual concentration of chlorophyll-a was high: 74.8 μg L⁻¹ (2002) and 61.4 μg L⁻¹ (2003). Mean seasonal zooplankton wet biomass varied from 92.5 g m⁻³ (2002) and 44.10 g m⁻³ (2003). In 2002 the planktonic crustaceans predominated; their mean biomass was 87.1 g m⁻³ and B. longirostris formed more than 91% of this value. In 2003, the zooplankton density was high (15,687 N L⁻¹), when rotifers contributed up to 94% of this value. The boom of rotifers (58,740 N L⁻¹) was recorded in June 2003. In total, 45 cladoceran and 14 copepod species were recorded in the medial and littoral zones. During observation we concluded that the structure of zooplankton, particularly species composition, abundance, biomass and seasonal dynamics are affected by the fluctuation of water levels in the arms of the rivers’ inundation areas. This unstable hydrological regime prevented the development of planktonic crustaceans.     

Increasing fish production from wetlands at Lake Victoria, Uganda using organically manured seasonal wetland fish ponds

The processes driving primary productivity and its impacts on fish production were investigated in field trials in eight seasonal earthen wetland ponds ‘Fingerponds’ (192 m²) in Uganda between 2003 and 2005. The ponds were stocked by the seasonal flood with predominantly Oreochromis spp. at densities ranging from 0.1 to 0.5 fish m⁻². Chicken manure (521, 833 or 1,563 kg ha⁻¹) was applied fortnightly. Results showed that primary productivity was enhanced with maximum average net primary productivity (±Standard Error) of 11.7 (±2.5) g O₂ m⁻² day⁻¹ at the Gaba site and 8.3 (±1.5) g O₂ m⁻² day⁻¹ at the Walukuba site. Net fish yields were higher in manured ponds with up to 2,670 kg ha⁻¹ yield for a 310 day growth period compared to less than 700 kg ha⁻¹ in unmanured ponds. Fish production was limited mainly by high recruitment, falling water levels, light limitation from high suspended solids and turbidity, and low zooplankton biomass. It was concluded that Fingerponds have a high potential for sustainable fish production and can contribute to the alleviation of protein shortages amongst the riparian communities around Lake Victoria. Production can be enhanced further with improved stock management.     

Feeding at different plankton densities alters invasive bighead carp (<Emphasis Type="Italic">Hypophthalmichthys nobilis</Emphasis>) growth and zooplankton species composition

Invasive Asian carps Hypophthalmichthys spp. are an ecological threat to non-native aquatic ecosystems throughout the world, and are poised to enter the Laurentian Great Lakes. Little is known about how these filter-feeding planktivores grow and impact zooplankton communities in mesotrophic to oligotrophic systems like the Great Lakes. Our purpose was to determine how different plankton densities affect bighead carp H. nobilis biomass and how bighead carp affect zooplankton species composition. We conducted a 37-day indoor mesocosm experiment (volume = 678 l) with high and low plankton treatments (zooplankton dry mass ≈ 1,900 and 700 μg l⁻¹; chlorophyll a = 25 and 14 μg l⁻¹, respectively) in the presence and absence of juvenile bighead carp (mean = 5.0 g, 8.5 cm). Carp lost weight in the low plankton treatment and gained weight in the high plankton treatment, suggesting that food availability may be a limiting factor to bighead carp growth in regions of low plankton densities. In the presence of carp, zooplankton shifted from Daphnia to copepod dominance, while in the absence of carp, Daphnia remained dominant. Chydorids and ostracods increased in the presence of carp, but only in the low plankton treatment, suggesting that the impact of bighead carp on zooplankton species composition may vary with zooplankton density. Chlorophyll was higher in the absence of carp than in the presence. Chlorophyll and zooplankton densities in many Great Lakes ecosystems are substantially lower than our low treatment conditions, and thus our results suggest that Asian carp establishment in these regions may be unlikely. Handling editor: S. Declerck     

Trophic importance of the hyperiid amphipod, Themisto gaudichaudi, in the Prince Edward Archipelago (Southern Ocean) ecosystem

The feeding dynamics and predation impact of the hyperiid amphipod, Themisto gaudichaudi, on the zooplankton community in the waters surrounding the Prince Edward Archipelago were investigated at 30 stations in late austral summer (April/May) 1998. Ingestion rates of T. gaudichaudi were estimated using two approaches, the gut fullness index and in vitro incubations. Throughout the investigation mesozooplankton, comprising copepods, pteropods and chaetognaths, numerically and by biomass dominated Bongo samples. Zooplankton abundances and biomass ranged from 8 to 271 ind. m⁻³ and between 1.01 and 7.47 mg dwt m⁻³, respectively. Densities of T. gaudichaudi during the study were low, never exceeding 0.4 ind. m⁻³. Gut content analysis (n=61) indicates that T. gaudichaudi is a non-selective, opportunistic carnivore generally feeding on the most abundant copepod and chaetognath species. Peaks in feeding activity were recorded at sunrise and sunset, corresponding to their diel vertical migration patterns. Daily rations estimated from in vitro incubations and gut fullness index were equivalent to 1.2–8.7% and between 11.5 and 19.8% of body dry weight, respectively. The predation impact of T. gaudichaudi averaged over the upper 300 m of the water column was low, accounting for <0.4% of the mesozooplankton biomass or <3% of the mesozooplankton secondary production. Indeed, the predation impact is likely to be lower as the contribution of the smaller copepods (e.g. Oithona spp.) to total zooplankton was underestimated due to the sampling gear employed. The low predation impact recorded during this study can be related to low abundances of T. gaudichaudi. It is likely that the importance of T. gaudichaudi as a secondary production consumer in the waters surrounding the Prince Edward Archipelago demonstrates a high degree of spatio-temporal variability. Accepted: 6 December 1999     

Mesozooplankton structure in the northern White Sea in July 2008

The mesozooplankton of the northern White Sea and Mezen Bay was investigated at nine stations in July 2008 using a Juday net (168 μm mesh size). A total of 39 taxa (species and higher taxa) were found in the samples. Average abundance, biomass, and diversity (Shannon index) were (±SE) 120,793 ± 70,439 ind. m⁻², 443 ± 216 mg DW m⁻², and 1.41 ± 0.11, respectively. Copepods were most numerous. Overall, herbivores dominated primarily Cirripedia nauplii and Pseudocalanus minutus. Significant correlations were observed among mean temperature, salinity, and mean mesozooplankton abundance and biomass. Our data suggest that salinity and intensive local currents could be the main factors responsible for the distribution of mesozooplankton in the northern White Sea. The average mesozooplankton biomass was higher than in previous studies, indicating a possible climatic impact on the mesozooplankton community.     

Mesozooplankton distribution in northern Svalbard waters in relation to hydrography

We investigated the distribution of mesozooplankton in waters north of Svalbard (north of 78°50′N) at 38 stations in August and September of 2002, 2003 and 2004. The zooplankton community was numerically dominated by copepods (58–98% of the total abundance). Zooplankton abundance ranged from 115 individuals m⁻³ at the northern most location to 12,296 individuals m⁻³ on the shelf. Cluster analysis revealed four different groups with distinct geographic integrity that were identified by variation in species densities rather than by variation in taxonomic composition. Water temperature and salinity differed significantly between the different cluster groups indicating that part of the observed variations in species distribution relate to differences in hydrography. Numerous significant regressions between zooplankton abundance at species level and hydrographical parameters suggest that variability in water masses has measurable effects on zooplankton distribution and species composition in the study area.     

Year-to-year changes of the mesozooplankton community in the Chukchi Sea during summers of 1991, 1992 and 2007, 2008

A recent drastic decrease in sea ice cover area was observed in the western Arctic Ocean during summer, yet little information is available for its effect on zooplankton community. To evaluate the effect of sea ice reduction on zooplankton, we studied year-to-year changes of zooplankton community structure in the Chukchi Sea during summers of 1991, 1992 (when sea ice extended), 2007, and 2008 (when sea ice reduced). Zooplankton abundance ranged from 4,000 to 316,000 ind. m⁻² (mean: 70,000) and was greater north of Lisburne Peninsula in 2008. Zooplankton biomass ranged from 0.07 to 286 g wet mass m⁻² (mean: 36) and was greater south of Lisburne Peninsula in 2007. Cluster analysis based on zooplankton abundance showed a division of the zooplankton community into four groups. Occurrence of each group was separated geographically and interannually, and geographic distributions of each group in 1991 and 1992 were similar but those in 2007 and 2008 were shifted northward. Abundance and biomass in 2007/2008 were higher than in 1991/1992, indicating that further sea ice reduction would have a positive effect on zooplankton production (e.g. invasion of large Pacific species and temperature effects on their growth rate). The northern shift in geographic distribution of the zooplankton community in 2007/2008 indicates that sea ice reduction would have a negative effect on the zooplankton community (loss of characteristic Arctic species) in part of the Chukchi Sea. These apparently contradictory effects of sea ice reduction on zooplankton community emphasize the critical need for continued monitoring in this area.     

Response of the plankton community to herbicide application (triazine herbicide,simetryn) in a eutrophicated system: short-term exposure experiment using microcosms

The methylthiotriazine herbicide, simetryn, is commonly used in Japan, and its concentration in surface water is often high enough to affect natural phytoplankton. To estimate how the plankton community in eutrophic systems respond to short-term exposure of realistic concentrations of simetryn, we collected plankton from a eutrophic lake and exposed them to low (20 μg l⁻¹) and high (100 μg l⁻¹) concentrations of simetryn for 12 days in microcosm tanks (50 l). High concentrations significantly lowered total phytoplankton biomass, particularly green algal density. Consequently, the species composition was severely modified by simetryn application. However, there was no apparent impact of simetryn on microbial food-web components, bacteria, heterotrophic nanoflagellates (HNF), and ciliates. Despite the decreased abundance of algal food, the zooplankton community showed subtle changes with simetryn application. The results indicate that the direct impact of simetryn on planktonic organisms other than phytoplankton, particularly on microbial food-web components, is weak. The indirect impact of simetryn on zooplankton through the change of food quality and quantity was also small. It has been suggested that the persistence of microorganisms, alternative food for zooplankton, probably dilutes the indirect impact of simetryn on zooplankton by compensating for the loss of food phytoplankton. Consequently, the plankton community in eutrophicated systems is resistant to the herbicide at a feasible concentration for a short period of time.     

First record of sympagic hydroids (Hydrozoa,Cnidaria) in Arctic coastal fast ice

We report on the first record of interstitial cnidarians in sea ice. Ice core samples were collected during eight field periods between February 2003 and June 2006 in the coastal fast ice off Barrow, Alaska (71°N, 156°W) at four locations. A total of 194 solitary, small (0.2–1.1 mm) elongated specimens of a previously unknown interstitial hydroid taxon were found. By cnidome composition and the occurrence of a highly retractable pedal disc formed by epidermal tissue only, the specimens are tentatively assigned to representatives of the family Protohydridae, subclass Anthomedusae. The hydroids were found almost exclusively in the bottom 10 cm-layer (at the ice–water interface) of 118 ice cores, with abundances ranging from 0 to 27 individuals per core section (0–4,244 ind m⁻²) and a grand mean of 269 ind m⁻² in bottom 10 cm-layer sections. Abundances were lower in December and late May than in months in between with considerable site variability. A factor analysis using 12 variables showed that hydroid abundance correlated highest with abundances of copepod nauplii and polychaete juveniles suggesting a trophic relationship.     

Structure and grazing impact of the mesozooplankton community during late summer 1994 near South Georgia, Antarctica

Mesozooplankton abundance, community structure and grazing impact were determined during late austral summer (February/March) 1994 at eight oceanic stations near South Georgia using samples collected with a Bongo and WP-2 nets in the upper 200-m and 100-m layer, respectively. The zooplankton abundance was generally dominated by copepodite stages C3–C5 of six copepod species: Rhincalanus gigas, Calanus simillimus, Calanoides acutus, Metridia spp., Clausocalanus laticeps and Ctenocalanus vanus. Most copepods had large lipid sacs. All copepods accounted for 41–98% of total zooplankton abundance. Juvenile euphausiids were the second most important component contributing between 1 and 20% of total abundance. Pteropods, mainly Limacina inflata, were important members of the pelagic community at two sites, accounting for 44 and 53% of total abundance. Average mesozooplankton biomass in the upper 200 m was 8.0 g dry weight m⁻², ranging from 4.3 to 11.5 g dry weight m⁻². With the exception of Calanussimillimus, gut pigment contents and feeding activity of copepod species were low, suggesting that some species, after having stored large lipid reserves, had probably started undergoing developmental arrest. Daily mesozooplankton grazing impact, measured using in situ gut fluorescence techniques and in vitro incubations, varied widely from <1 to 8% (mean 3.5%) of phytoplankton standing stock, and from 5 to 102% (mean 36%) of primary production. The highest grazing impact was found northeast of the island co-incident with the lowest phytoplankton biomass and primary production levels. Received: 30 October 1996 / Accepted: 23 February 1997     

Instability of the turbidity maximum in the macrotidal Geum River estuary, western Korea

In the low-salinity area of many macrotidal estuaries, through the combination of tidal pumping and estuarine circulation, an estuarine turbidity maximum (ETM) develops providing favorable conditions for various organisms. To investigate ecological roles of the ETM in East Asian estuaries, we conducted seasonal observations in the Geum (or Keum) River estuary, one of the representative macrotidal estuaries flowing into the Yellow Sea, from 2007 to 2008. The estuary was frequently filled with high-salinity (>10 PSU) and low-turbidity (<100 NTU) water under small or no freshwater discharge from a dam (ca. 8 km upstream from the river mouth). Brackish water was, however, completely pushed out of the estuary within a few hours after an intensive discharge in summer. Chlorophyll a (up to 50 μg l⁻¹) and pheophytin (up to 80 μg l⁻¹) were concentrated in a low-salinity (<1 PSU) and high-turbidity (up to 1000 NTU) area, indicating that the intensive discharge transported both living phytoplankton and resuspended detritus into the area. In contrast, a phytoplankton bloom (chlorophyll a, up to 100 μg l⁻¹) was observed at low salinities under little discharge in winter. The present study demonstrated an absence of the ETM suitable for estuarine-dependent organisms from the present Geum River estuary, indicating potential importance of adequate control of freshwater discharge for the formation and maintenance of the ETM.     

Estimating specific inherent optical properties of tropical coastal waters using bio-optical model inversion and in situ measurements: case of the Berau estuary,East Kalimantan,Indonesia

Specific inherent optical properties (SIOP) of the Berau coastal waters were derived from in situ measurements and inversion of an ocean color model. Field measurements of water-leaving reflectance, total suspended matter (TSM), and chlorophyll a (Chl a) concentrations were carried out during the 2007 dry season. The highest values for SIOP were found in the turbid waters, decreasing in value when moving toward offshore waters. The specific backscattering coefficient of TSM varied by an order of magnitude and ranged from 0.003 m² g⁻¹, for clear open ocean waters, to 0.020 m² g⁻¹, for turbid waters. On the other hand, the specific absorption coefficient of Chl a was relatively constant over the whole study area and ranged from 0.022 m² mg⁻¹, for the turbid shallow estuary waters, to 0.027 m² mg⁻¹, for deeper shelf edge ocean waters. The spectral slope of colored dissolved organic matter light absorption was also derived with values ranging from 0.015 to 0.011 nm⁻¹. These original derived values of SIOP in the Berau estuary form a corner stone for future estimation of TSM and Chl a concentration from remote sensing data in tropical equatorial waters.     

Distribution and factors influencing on structure of reef fish communities in Nha Trang Bay Marine Protected Area, South-Central Vietnam

Visual censuses of coral reef fishes in Nha Trang Bay Marine Protected Area (MPA) were conducted during September–October 2005. Nha Trang Bay MPA is relatively rich in reef fishes compared to other areas in Vietnam and the Pacific Ocean outside the ‘Coral Triangle,’ consistent with its biogeographic location in the western South China Sea. A total of 266 species of 40 families of coral reef fishes formed five distinct assemblages. Spatial variations in distribution and structure of the assemblages were associated with eight significant biological and physical variables which were cover of living hard corals, encrusting corals, branching corals, Acropora, Millepora, Montipora, depth and distance from the coast of the mainland. The six factors in front are likely related to provision of shelter and nutrition, while the distance factor is likely to represent a gradient in disturbance and impacts from various mainland sources including sedimentation and pollution discharge from nearby rivers. Local species richness ranged from 35 to 70 species 500 m⁻² (mean: 51 ± 2 SE) for reef flat stations and from 23 to 68 species 500 m⁻² (mean: 48 ± 4 SE) for reef slope stations. Total species richness at each site averaged 76 species (±4 SE), ranging from 56 to 110 species, dominated by wrasses, damselfishes, butterflyfishes, parrotfishes, surgeonfishes, groupers and goatfishes. Density of total fishes at each station ranged from 348 to 1,444 individuals 500 m⁻² (mean: 722 ± 302 SE) for the reef flat stations and from 252 to 929 individuals 500 m⁻² (mean: 536 ± 215.7 SE) for the reef slope stations. Overall mean density at each site averaged 628.9 (±238.4 SE) individuals 500 m⁻². The highly protected sites supported higher mean density of fishes per site (ranged: 904.5–1,213 individuals 500 m⁻² for Hon Mun and 1,167.5 individuals 500 m⁻² for Hon Cau) compared to other sites (<800 individuals 500 m⁻²). Of the families included in the census, densities were dominated throughout the MPA by damselfishes and wrasses. Many target species, particularly groupers, snappers and emperors, were rare or absent and the low abundance of big fishes was consistent with over-harvesting. Similarly a low density of butterfly fishes and angelfishes is likely related to the supply for marine aquaria in Vietnam and overseas. This study provides an important baseline against which the success of present and future MPA management initiatives may be assessed.     

Summer mesozooplankton distribution near Novaya Zemlya (eastern Barents Sea)

Regional variations in mesozooplankton composition, abundance and biomass were studied during a cruise in August 2006 near Novaya Zemlya Archipelago (eastern Barents Sea) using Juday net hauls from the bottom (or 100 m depth) to the surface. A comparison with multiannual literature values revealed that the mean temperature and salinity in the south and centre of the study area were similar to typical values, while temperature in the north was significantly higher. A total of 36 species and higher taxa were identified. Mesozooplankton abundance and biomass varied from 47 to 851 ind m⁻³ and from 5 to 74 mg dry weight m⁻³, respectively. Copepods dominated the mesozooplankton community, reaching 73–98% and 61–97% of the total abundance and biomass. Calanus finmarchicus and Oithona similis were the most abundant species at all stations. The biodiversities (Shannon indices) of the mesozooplankton community varied between stations from 1.10 to 2.46 (estimated from species abundances) and from 0.19 to 1.92 (estimated from species biomasses), averaging 1.93 ± 0.127 and 1.34 ± 0.151, respectively. Three groups at the 48% level of dissimilarity of species abundance were delineated by cluster analyses. The clusters differed significantly with respect to temperature and salinity. The total mesozooplankton abundance and biomass as well as quantitative parameters of most common taxa scaled negatively with temperature.