High Zooplankton Abundance Research Articles

Impacts of Colombo-Katunayake Expressway Bridge Opening on Water Quality at Madabokka in Negambo Lagoon, West Coast of Sri Lanka

The proposed 5 year Colombo- Katunayake expressway construction project which is targetto reduce travelling time between Colombo and Katunayake international airport in SriLanka. This project would build 42 bridges and 88 culverts. One of the bridges opened atMadabokka inside the Negambo Lagoon is identified as highly productive ecosystem whichprovides breeding, feeding and security grounds for variety of aquatic lives. Thus, currentStudy the seasonal impact on Madabokka is carried out using water quality analysis.Water samples from nine locations of three main sites (southern side, Northern side andoutside of the Madabokka) are analysed for physical, (temperature, salinity, pH andtransparency or sechchi depth) chemical, [NO3, NO2, PO4, SiO2, Total suspended solids(TSS), and Dissolved Oxygen (DO)], and biological parameters (chlorophyll a,phytoplankton and zooplankton) once in two months during the year 2012.Results indicate that average salinity and temperature are varied from 14.24-24.54 PSU and310C (September) – 340C (March) respectively, while the warmest water is existed insouthern part of Maddabokka which has no free exchange with Negambo lagoon. However,the observed spatial and temporal variation would be related to climatic conditions ratherthan bridge constructions. Both the lowest (4.6) and the highest values (7.9) pH values andwere recorded outside Maddabokka during June and March respectively. Low pH values inmonth of June would be associated with South-West monsoon and particular low valuescould be a result of fresh water runoff canals from Katunayake airport area. Sechchi depth isalways ≤ 1.00m and higher depth remained as turbid water due to rapid constructions. DOvalues are varied from 5.9 - 8.3 mg l-1 with no impacts from the bridge constructions. TSSvalues are varied from 13.9-84.3 mg l-1 and the highest value is recorded in southern side ofthe bridge during November. Level of nutrients, (Nitrite; 0.05-5.34 mg l-1, Nitrate; 0.06-0.17mgl-1, Phosphate; 0.00-0.84 mg l-1, Silicates; 2.68-14.88 mg l-1) are varied temporally andthere is no construction interferences. Chlorophyll a (1.10-20.51 mg l-1) is distinctive intemporally and no spatial variations. The highest abundance (355000 Ind/L) of Phytoplanktonare recorded in Southern side of the bridge in March. All guilds were dominated by centricdiatoms. The lowest and the highest Zooplankton abundance (27 ind/l and 530 ind/L) arerecorded at outside of Madabokka during March and September respectively. Speciesdiversity (7 groups) is high in southern part of the Madabokka and dominated by Calanoids inJune and November.

Association between pygmy right whales (Caperea marginata) and areas of high marine productivity off Australia and New Zealand

Opportunistic sightings and strandings of Caperea marginata (n=196) from the vicinity of Australia and New Zealand (1884 to early 2007) were used to relate geographic and temporal patterns to oceanographic and broad-scale climatic variability. Records were not uniformly distributed along the coast and more (69%) were from Australia than New Zealand. Seven coastal whale ‘hotspots’ were identified which accounted for 61% of records with locality data. Half of the hotspot records were from southeast (37) and northwest (20) Tasmania—others each had 9–15 events. Upwelling and/or high zooplankton abundance has been documented near all whale hotspots. Records of C. marginata occurred in all months, with 75% in spring and summer. Inter-annual variability showed broad agreement between increased whale records (usually in spring/summer) and strongly positive ‘Niño 3.4’ during 1980–1995 but not thereafter. Coastal upwelling and productivity increase during climatic phenomena such as El Niño and are likely to be quickly beneficial to plankton-feeding whales such as C. marginata.

Distribution patterns of micro- and meso-zooplankton communities in sea ice regions of Lützow-Holm Bay, East Antarctica

In the Southern Ocean, zooplankton research has focused on krill and macro-zooplankton despite the high densities of micro- and meso-zooplankton. We investigated their community structure in relation to different sea ice conditions around Japan’s Syowa Station in Lutzow-Holm Bay, in the summers of 2011 and 2012. Zooplankton samples were collected using vertical hauls (0–150 m), with a closing net of 100-μm mesh size. The results of cluster analysis showed that the communities in this region were separated into fast ice, pack ice, and open ocean fauna. The fast ice fauna had lower zooplankton abundance (393.8–958.9 inds. m−3) and was dominated by cyclopoid copepods of Oncaea spp. (54.9–74.8 %) and Oithona similis (6.6–19.9 %). Deep-water calanoid copepods were also found at the fast ice stations. Pack ice and open ocean fauna had higher zooplankton abundance (943.6–2,639.8 inds. m−3) and were characterized by a high density of foraminiferans in both years (6.6–61.9 %). Their test size distribution indicated that these organisms were possibly released from melting sea ice. The pteropod Limacina spp. was a major contributor to total abundance of zooplankton in the open ocean zone in 2012 (26.4 %). The physical and/or biological changes between 2 years may affect the abundance and distribution of the dominant zooplankton taxa such as cyclopoid copepods, foraminiferans, and pteropods. Information on the relationships between the different species associated with sea ice will help to infer the possible future impacts of climate change on the sea ice regions.

Zooplankton species richness–productivity relationship: Confronting monotonic positive and hump‐shaped models from a local perspective

AbstractThis study examined two models that are most frequently used to describe the relationship between species richness and productivity (SPR): monotonic positive and hump‐shaped models. We assessed zooplankton community diversity in response to algal productivity. The relationship between net primary productivity (NPP) and rarefied species richness was examined by fitting the data to two models and comparing them using the Akaike information criterion (AICc). Macrophyte banks with the highest net primary productivity had the highest zooplankton abundance. Our results pointed to a hump‐shaped model as the best fit to describe the relationship between zooplankton species richness and primary productivity (ΔAICc > 4). Thus, the diversity was lower at the extremes of productivity and higher at intermediate levels of productivity. We suggest that this relationship might occur because when the resource supply rates are low, environmental conditions are stressful, whereas a high availability of resources enhances competitive exclusion. Two observations supported this statement: (i) the total abundance of the community positively correlated with NPP (P < 0.05), indicating that less productive sites had few consumers and the raised productivity tended to favour the total abundance; (ii) NPP was negatively correlated with evenness (P < 0.05), indicating that productivity increased the dominance of certain species in the communities. Therefore, we challenged two of the models most frequently used to explain SPR, and discuss some mechanisms underlying a hump‐shaped SPR.

Trophic efficiency of plankton food webs: Observations from the Gulf of Mannar and the Palk Bay, Southeast Coast of India

This paper introduces the structure and trophic efficiency of plankton food webs in the Gulf of Mannar (GoM) and the Palk Bay (PB) — two least studied marine environments located between India and Sri Lanka. The study is based on the results obtained from a field sampling exercise carried out in the GoM and the PB in March 2010 (Spring Intermonsoon — SIM), September 2010 (Southwest Monsoon — SWM) and January 2011 (Northeast Monsoon — NEM). Based on multivariate analysis of major environmental parameters during different seasons, it was possible to clearly segregate the GoM and the PB into separate clusters, except during the SWM. This segregation of the GoM and the PB was closely linked with the seasonally reversing ocean currents in the region, as evident from the MIKE 21 flow model results. During the period of relatively low phytoplankton biomass (<23mgCm−3), the organic carbon contribution of the microbial loop was significantly high — both in the GoM and the PB. During the SIM, the carbon biomass available in the plankton food web was significantly higher in the PB (av. 122.8±47.60mgCm−3) than in the GoM (av. 81.89±35.50mgCm−3). This was due to a strong microbial loop in the former region. In the GoM, phytoplankton contributed a considerable portion (>50%) of the carbon biomass during the SWM and the NEM, whereas, microbial loop contributed significantly (80%) during the SIM. The microbial loop was predominant in the PB throughout the study period, being as high as 83% of the total plankton biomass during the SIM. As compared to the PB, the mesozooplankton biomass was higher in the GoM during the SWM and the NEM and lower during the SIM. The relatively high mesozooplankton stock in the PB during the SIM was closely linked with a strong microbial loop, which contributed the major share (av. 101.6±24.3mgCm−3) of the total organic carbon available in the food web (av. 126.6±24.3mgCm−3). However, when microbial loop contributed >65% of the total organic carbon available in the food web, the trophic efficiency was found to be low (~3%), which can be attributed to the wide dispersal of organic carbon in the microbial loop. Importantly, during the NEM, when the copepod Paracalanus parvus was predominant in the PB, the trophic efficiency of the microbial loop dominant food web increased by more than a fold (7.2%). The study provides evidences for the first time from the field that exceptionally high abundance of efficient microzooplankton-consuming zooplankton can significantly increase the trophic efficiency of the microbial loop dominant plankton food web.

ZOOPLANKTON SPATIAL DISTRIBUTION AND COMMUNITY STRUCTURE IN BANGGAI SEA

&lt;p&gt;Banggai Sea is an interesting ecosystem due to mixing influences from Banda Sea in the west and Maluccas Sea in the east. Therefore, a unique zooplankton community structure and specific distribution pattern should be found in this area. This research was carried on using Baruna Jaya VIII research vessel and samples were collected in 14 sampling stations. Vertical towing using NORPAC plankton net (300 μm) was conducted to collect zooplankton samples. Result showed that inner Mesamat Bay had the lowest abundance of zooplankton, probably due to low water quality resulted from anthropogenic activity. Meanwhile the strait between Liang and Labobo Island had the highest zooplankton abundance in Banggai Sea. Calanoids was the dominant zooplankton taxa in the ecosystem and contributing 55.7% of total density of zooplankton community. The highest importance value made this taxa to be very important factor that regulates the lower trophic level organisms. Results also showed that zooplankton was distributed nearly uniform in eastern but aggregated to several stations in western Banggai Sea. Zooplankton abundance was higher in the central of Banggai Sea, compared to western and eastern area. According to Bray-Curtis clustering analysis the strait between Liang and Labobo Island has unique zooplankton community structure. This might happened due to mixing of water from two highly productive seas that influenced the Banggai Sea ecosystem. From this research we conclude that this strait probably was the zooplankton hot spot area which might also indicate that this area also a hot spot of fishes in the Banggai Sea.&lt;/p&gt;&lt;p&gt;Keywords: spatial distribution, zooplankton, community structure, hot spot, Banggai&lt;/p&gt;

ZOOPLANKTON SPATIAL DISTRIBUTION AND COMMUNITY STRUCTURE IN BANGGAI SEA

Banggai Sea is an interesting ecosystem due to mixing influences from Banda Sea in the west and Maluccas Sea in the east. Therefore, a unique zooplankton community structure and specific distribution pattern should be found in this area. This research was carried on using Baruna Jaya VIII research vessel and samples were collected in 14 sampling stations. Vertical towing using NORPAC plankton net (300 μm) was conducted to collect zooplankton samples. Result showed that inner Mesamat Bay had the lowest abundance of zooplankton, probably due to low water quality resulted from anthropogenic activity. Meanwhile the strait between Liang and Labobo Island had the highest zooplankton abundance in Banggai Sea. Calanoids was the dominant zooplankton taxa in the ecosystem and contributing 55.7% of total density of zooplankton community. The highest importance value made this taxa to be very important factor that regulates the lower trophic level organisms. Results also showed that zooplankton was distributed nearly uniform in eastern but aggregated to several stations in western Banggai Sea. Zooplankton abundance was higher in the central of Banggai Sea, compared to western and eastern area. According to Bray-Curtis clustering analysis the strait between Liang and Labobo Island has unique zooplankton community structure. This might happened due to mixing of water from two highly productive seas that influenced the Banggai Sea ecosystem. From this research we conclude that this strait probably was the zooplankton hot spot area which might also indicate that this area also a hot spot of fishes in the Banggai Sea.Keywords: spatial distribution, zooplankton, community structure, hot spot, Banggai

Seasonal and interannual variation in the planktonic communities of the northeastern Chukchi Sea during the summer and early fall

We analyzed the seasonal and interannual variability of the planktonic communities in a densely sampled region of the northeastern Chukchi Sea as part of a multidisciplinary ecosystem study from 2008 to 2010. Observations of chlorophyll-a, inorganic macronutrients, and zooplankton (using both 150-μm and 505-μm mesh nets) were made within two 900-NM 2 grids (Klondike and Burger) at high spatial resolution three times each in 2008 and 2009, with a third grid (Statoil) sampled twice in 2010. Sea-ice conditions prior to sampling varied notably during the study: seasonal sea ice retreat was earlier and sea-surface temperatures (SSTs) were warmer in 2009 than in 2008, whereas SSTs for 2010 were intermediate between the 2008 and 2009 values. Eighty taxonomic categories of zooplankton, including 11 meroplanktonic categories, were recorded, with the greatest diversity found within the copepods (25 species), followed by the cnidarians (11 species). All species are typical for the region and most are seeded from the Bering Sea. A seasonal progression of the community structure was apparent over each survey area and was likely influenced by temperature. Cold oceanographic conditions in 2008 likely slowed growth and development of the zooplankton, such that holozooplankton abundance averaged 2389 and 106 individualsm–3 and biomass averaged 10.5 and 8.3mgDWm–3 in the 150- and 505-μm nets, respectively. An early phytoplankton bloom in 2009 apparently supported a zooplankton community of greater abundance, but moderate biomass, averaging 6842 and 189 individualsm–3, and 16.3 and 7.0mgDWm–3 in the 150- and 505-μm nets, respectively. Highest zooplankton abundance and biomass values among the three years occurred in 2010: 7396 and 198 individualsm–3 and 102.9 and 33.5mgDWm–3 in the 150- and 505-μm nets, respectively. Holozooplankton biomass changes were driven by increases in large-bodied, lipid-rich copepods. The contribution of meroplankton was substantial in this shallow-water ecosystem: numerically, they contributed 28% in 2008, 8% in 2009 and 56% in 2010 to the total zooplankton community and 43%, 27%, and 11%, respectively, terms of biomass for the 150-μm nets. Interannual differences in ice-melt timing, water temperatures, northward transport of water masses, and nutrients and chlorophyll concentrations resulted in highly variable pelagic productivity.

POTENTIAL ROLES OF BIOTIC FACTORS IN REGULATING ZOOPLANKTON COMMUNITY DYNAMICS IN JAKARTA BAY SHALLOW WATER COASTAL ECOSYSTEM

&lt;p&gt;The dynamics in zooplankton abundance were regulated by changes in water physical-chemical parameters and interaction with biotic factors. In this research we examined the relationship between zooplankton community dynamic and important biotic factors, such as predation and food availability, in Jakarta bay. Plankton samplings were done in 10 sampling stations in Jakarta bay, from July to November 2009. Zooplankton samples were collected using horizontal towing method with NORPAC plankton net (mesh size 300 μm). Salinity, water depth, water temperature, and water transparency were measured. Phytoplankton samples were also collected with the same method as zooplankton, using Kitahara plankton net (mesh size 80 μm). Zooplankton taxas were grouped into two groups, the prey and predatory zooplankton. The results showed that there were two different patterns in zooplankton groups dynamic i.e., the single and double peak. The abundance peak in most zooplankton groups, such as copepods, cirripeds, luciferids, and tunicates, were induced by the high food availability during the phytoplankton bloom in August. The high abundance of prey zooplankton groups in August was responded by the predatory zooplankton groups, resulting in high abundance of predatory zooplankton in adjacent month. The high abundance of ctenophores and chordates (fish larvae) were suggested as the main factor for the low abundance of other zooplankton in September. Physical and chemical factors were not the regulating factors due to the stability of those factors during this research period. Thus we concluded that food availability and predator-prey interaction were the main factors which regulate zooplankton community dynamics in Jakarta bay.&lt;/p&gt;&lt;p&gt;Keywords: predator-prey interaction, zooplankton, abundance peak, food availability, phytoplankton bloom&lt;/p&gt;

POTENTIAL ROLES OF BIOTIC FACTORS IN REGULATING ZOOPLANKTON COMMUNITY DYNAMICS IN JAKARTA BAY SHALLOW WATER COASTAL ECOSYSTEM

The dynamics in zooplankton abundance were regulated by changes in water physical-chemical parameters and interaction with biotic factors. In this research we examined the relationship between zooplankton community dynamic and important biotic factors, such as predation and food availability, in Jakarta bay. Plankton samplings were done in 10 sampling stations in Jakarta bay, from July to November 2009. Zooplankton samples were collected using horizontal towing method with NORPAC plankton net (mesh size 300 μm). Salinity, water depth, water temperature, and water transparency were measured. Phytoplankton samples were also collected with the same method as zooplankton, using Kitahara plankton net (mesh size 80 μm). Zooplankton taxas were grouped into two groups, the prey and predatory zooplankton. The results showed that there were two different patterns in zooplankton groups dynamic i.e., the single and double peak. The abundance peak in most zooplankton groups, such as copepods, cirripeds, luciferids, and tunicates, were induced by the high food availability during the phytoplankton bloom in August. The high abundance of prey zooplankton groups in August was responded by the predatory zooplankton groups, resulting in high abundance of predatory zooplankton in adjacent month. The high abundance of ctenophores and chordates (fish larvae) were suggested as the main factor for the low abundance of other zooplankton in September. Physical and chemical factors were not the regulating factors due to the stability of those factors during this research period. Thus we concluded that food availability and predator-prey interaction were the main factors which regulate zooplankton community dynamics in Jakarta bay.Keywords: predator-prey interaction, zooplankton, abundance peak, food availability, phytoplankton bloom

Submerged macrophytes as a habitat for zooplankton development in two reservoirs of a flow-through system (Papuk Nature Park, Croatia)

In order to determine the influence of lentic habitats and macrophyte stands on the plankton development and seston flux, an investigation of zooplankton was carried out in the karst Jankovac flow- through system (Papuk Nature Park, Croatia). The system was characterized by low abundance (1-116 ind.L x1 ) and high diversity of identified zooplankton. Eighty-six taxa were recorded, comprising 57 rotifers, 15 cladocerans, 8 copepods and 6 members of other groups of organisms. The spatial oscillations of environ- mental parameters and biocoenosis assemblage revealed statistically significant differences between lotic and lentic habitats, as well as between vegetated and non-vegetated stations. These differences mainly respond to higher concentration of food resources and zooplankton/zooseston abundance and biomass in lentic, espe- cially vegetated, habitats. This is also proved by results of principal component analysis (PCA), which sug- gested that the main drivers of development of the planktonic community were the food resources and the avoidance of flow velocity. Accordingly, shoreline areas with submerged macrophyte stands of Hippuris vul- garis L. were the most productive parts, represented by highest zooplankton abundance, biomass and biodi- versity. Flow velocity significantly affected crustaceans assemblage, so that higher abundances of the larger cladocerans and copepods were achieved in vegetated stations with low flow velocity, while rotifers showed to be rheotolerance organisms. On the other hand, the longitudinal discontinuum of the stream channel by two man-made reservoirs could offer new habitats to enrich seston with organic particles and bioseston. The re- sults of our study pronounce the need for further monitoring of this hydrosystem, especially considering bio- diversity and microhabitats conservation.

Surface zooplankton distribution patterns during austral summer in the Indian sector of the Southern Ocean, south of Australia

We investigated the composition, distribution and abundance of micro- and mesozooplankton in the Southern Ocean, south of Australia during the austral summer (December–February) of the 2007/08 season using a Continuous Plankton Recorder (CPR). Four CPR tows were conducted during two separate oceanographic voyages under the CEAMARC (Collaborative East Antarctic Marine Census) project. High zooplankton abundance was recorded on each transect in the Polar Frontal Zone (PFZ) and the Inter Polar Frontal Zone (IPFZ). The community structure in these zones was dominated by common taxa including the ubiquitous small calanoid copepods, Oithona similis and Calanus simillimus, accounting for >70% of the total abundance, and copepod nauplii, foraminiferans and appendicularians of the genus Fritillaria spp. also occurred along most of the survey transects. Total zooplankton abundance was comparatively consistent along the four transects, and ranged between 119.8 and 144.7 ind m −3. The results of cluster and IndVal analyses revealed that the dominant species/taxa show similar associations, abundance and distribution patterns on all four transects. There was no evidence of a change of surface zooplankton abundance at the time of towing in this study. Detecting the various distribution patterns of micro- and mesozooplankton species/taxa, and the accumulation of high quality data collected by a consistent methodology will contribute to determining the consequences of climate change impacts on the ecosystem.

Spatial and temporal patterns in abundance and distribution of zooplankton in the Tanzanian waters of Lake Victoria

Zooplankton composition and abundance, and its spatial and temporal distribution patterns were investigated from September 2005 to October 2007 at 51 sampling stations at various depths in the near shore, intermediate, and offshore waters of Lake Victoria. Relative to near shore (54.86 ± 32.33 ind. l−1) and far offshore (38.63 ± 11.14 ind. l−1), the intermediate waters (109.56 ± 64.70 ind. l−1) had highest abundance of zooplankton. A total of 43 zooplankton species were encountered: of those 26 species were rotifers, with Brachionus angularis, Brachionus calyciflorus, and Asplanchna sp. as the most abundant species. There were 9 species of cladocerans, with Diaphanosoma excisum and Bosmina longirostris as the most abundant species. There were 7 cyclopoid species with Thermocyclops emini, Tropocyclops tenellus, and Thermocyclops neglectus as the most abundant species. Only one calanoid species, Thermodiaptomus galeboides was encountered. Cyclopoid copepods were the most abundant (76.5%) followed by calanoids (11.3%), rotifers (8%) and cladocerans (4.3%). The present findings contrast with earlier studies from the 1930s and 50s, but agree with many thereafter. There is change of zooplankton composition and abundance with a trend towards small sized species instead of the large. Increased eutrophications, pollution, and predation pressure from an increasing abundance of dagaa, juvenile perches, and reappearing haplochromines, among others, are responsible for the observed spatial and temporal variability in distribution and abundance patterns, and generally, change.

Downstream effects of beaver ponds on the water quality of New England first‐ and second‐order streams

AbstractBeaver, as allogenic ecosystem engineers, are capable of extensively altering surrounding habitats resulting in significant effects on stream water quality. This paper presents insight into downstream effects of beaver impoundments (both actively maintained and abandoned by beaver) and accumulated sediments on water quality, especially in protected watersheds serving as a drinking water supply. In a tributary un‐inhabited by beaver compared to those with active beaver ponds, we found significantly (p &lt; 0·001) lower concentrations of NO3N (respectively: mean (standard error)) without beaver 0·11 (0·005) mg/l and with beaver 0·14 (0·002) mg/l), NH4N (0·007 (0·002) and 0·24 (0·002) mg/l), dissolved organic carbon (DOC) (3·47 (0·081) and 8·37 (0·203) mg/l), chlorophyll (2·38 (0·066) and 6·96 (0·203) µg/l), and temperature (16·43 (0·101) and 19·85 (0·123) °C), but higher pH (7·17 (0·02) and 6·72 (0·022)), PO4 (0·20 (0·01) and 0·17 (0·014) mg/l) concentration, and dissolved oxygen (DO) saturation (100·8 (0·708) and 67·6 (1·74)%). Within the beaver ponds, we observed a high abundance of predatory zooplankton, which help to control algae and feed on detritus within the pond ecosystem. We intentionally breached an abandoned beaver dam in the field and conducted a sediment resuspension experiment in the laboratory to assess the potential for increases in turbidity and nutrients from beaver pond sediments as would be expected in the event of a catastrophic dam breach. We found that abandoned beaver ponds have a stronger influence on downstream water quality than actively maintained ponds owing to higher turbidity with finer sediments and sharply increased stream water temperature during a dam failure. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Differential effects of warming and nutrient loading on the timing and size of the spring zooplankton peak: an experimental approach with hypertrophic freshwater mesocosms

In shallow lakes, environmental warming and nutrient loading are important influences on the likelihood of a shift between clear and turbid ecosystem states. With temperatures and nutrient runoff predicted to increase within the next decades, climate change poses a threat to lake communities. However, current predictions on the effect of these environmental factors on the abundance and timing of peak zooplankton numbers are based on correlations rather than on experimental isolation of thermal from other confounding effects. We present results of warming (4°C above ambient) and increased nutrient loading on plankton communities in 48 outdoor mesocosms, simulating fishless and hypertrophic ponds. The timing of the chlorophyll a peak and crustacean zooplankton peak abundance, dominated by Daphnia pulex, responded strongly to temperature and nutrient addition. Daphnia numbers reached peaks 22–24 days earlier in heated than in unheated mesocosms. The chlorophyll a peak abundance advanced by 15–19 days with heating. Phytoplankton, total zooplankton and D. pulex reached peak abundance 12–19 days later when doses of nitrogen and phosphorus were added; this finding contradicts predicted earlier phytoplankton and zooplankton spring peak abundances with nutrient enrichment. Peak zooplankton and D. pulex abundances did not differ with temperature treatment, contrary to our expectations, but peak abundances occurred at similar actual temperatures. Nutrient additions had no effect on the peak zooplankton and D. pulex abundances in our mesocosms. Overall, climate warming is likely to advance plankton phenology in fishless ponds; however, this advance could be dampened in systems with high nutrient concentration. We found very high zooplankton abundances with warming and high nutrient loadings inducing a clear water state in all our tanks owing to heavy zooplankton grazing despite high nutrient concentrations.

Comparison of zooplankton distribution patterns between four seasons in the Indian Ocean sector of the Southern Ocean

We investigated the composition, distribution and abundance of zooplankton in the Indian Ocean sector of the Southern Ocean during the austral summer (December/January) of 2004/05, 2005/06, 2007/08 and 2008/09 using a Continuous Plankton Recorder (CPR). CPR tows were conducted along two transects during voyages south of Cape Town to north of Syowa station and from north of the Mawson station area to south of Fremantle. High zooplankton abundance was recorded on each transect in the Polar Frontal Zone (PFZ) and the northern area of the Antarctic Zone (AZ). Community structure in these zones was dominated by common taxa including the ubiquitous Oithona similis and calanoid copepodites, accounting for >50% of total abundance, and Calanus simillimus, Ctenocalanus citer, Clausocalanus laticeps and Metridia lucens also occurred in high densities. Appendicularians of the genus Fritillaria were the most important component in the Cape Town to Syowa station area in 2008, with 36.9% of total abundance. The average chlorophyll a level at this time of year was the lowest (0.32 mg m −3) among all transects. Appendicularians are suited to oceanic oligotrophic waters; therefore, they are suited to low phytoplankton density. Foraminiferans were numerically dominant throughout the Mawson station area to Fremantle transect in 2005. Unlike Fritillaria spp., foraminiferans prefer high phytoplankton density. The elevated average chlorophyll a biomass in 2005 (0.64 mg m −3) provided favorable conditions for Foraminifera, which were dominant and widespread. CPR surveys provide information on the fine scale structure of the inter-annual distribution changes in micro- and meso- zooplankton assemblages, and the CPR is one of ideal method to monitor organisms that are indicators of environmental change.

Surface zooplankton distribution in the Drake Passage recorded by Continuous Plankton Recorder (CPR) in late austral summer of 2000

We investigated the composition, distribution, and abundance of zooplankton in the Drake Passage in February 2000 using a Continuous Plankton Recorder. Zooplankton abundance varied considerably, between 1 and 1537 individuals/segment (where a segment is 5 nautical miles of surface towing) (mean ± SD = 121.3 ± 200.9). The highest abundances were recorded in the vicinity of the Polar Front (PF). Abundances increased at low latitudes north of the Sub-Antarctic Front (SAF) and decreased northward. A positive correlation was observed between zooplankton abundance and chlorophyll a concentration, reflecting the higher abundance of zooplankton north of the SAF, where higher abundances of phytoplankton were also observed. A total of 21 species/taxa of zooplankton were classified. Small calanoid copepods were found throughout the transect and accounted for 57.5% of total zooplankton abundance, followed by the Cyclopoid copepods Oithona spp. (25.9%) and Calanus simillimus (8.4%). The results of cluster analyses reveal that small calanoid copepods were the most important contributors to the high zooplankton abundance around the PF and north of the SAF in the Drake Passage. We suggest that a change in species composition has occurred since Hardy's descriptions in 1927, from abundant larger copepods and chaetognaths to smaller copepods and other species.

Influência da dieta sobre a abundância de Moenkhausia dichroura (Characiformes, Characidae) no reservatório de Manso, Estado de Mato Grosso

Este estudo teve por objetivo avaliar a dieta e abundância de Moenkhausia dichroura Kner, 1858 após a formação do reservatório de Manso, Estado de Mato Grosso. A dieta foi comparada espacial (montante, reservatório e jusante) e temporalmente (fase I, primeiro ano do represamento e fase II, quarto ano do represamento). Conteúdos estomacais de 392 indivíduos foram analisados e a dieta foi descrita através da representação volumétrica dos recursos alimentares. A montante a espécie mostrou tendência à insetivoria (V% = 51,46 de insetos aquáticos na fase I e V% = 56,07 de insetos terrestres na fase II), no reservatório à zooplanctivoria (V% = 77,11 e V% = 64,73 de microcrustáceos, nas fases I e II, respectivamente) e a jusante à herbivoria (V% = 56,02 e V% = 62,84 de vegetais, nas fases I e II, respectivamente). Constatou-se diferença espacial significativa na dieta (Kruskal-Wallis; H = 197,11, p &lt; 0,05), sendo também observada diferença temporal significativa entre as dietas dos indivíduos das estações montante I e montante II (teste a posteriori de comparação múltipla; p &lt; 0,05). Houve um aumento abrupto na abundância de M. dichroura durante o período de estudos, principalmente no quarto ano do represamento, no corpo principal do reservatório. Este fato parece estar estreitamente relacionado com a alta abundância e disponibilidade do zooplâncton no ambiente represado e também com a habilidade da espécie em explorar este recurso.

FLORAÇÕES DE CIANOBACTÉRIAS TÓXICAS EM UMA LAGOA COSTEIRA HIPEREUTRÓFICA DO RIO DE JANEIRO/RJ (BRASIL) E SUAS CONSEQUÊNCIAS PARA SAÚDE HUMANA

revista vol 13 no 2.indd Normal 0 21 false false false MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabela normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Times New Roman; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} The Jacarepagua Basin, Rio de Janeiro, Brazil has over the last four decades undergone a disordered process of urban and industrial growth with direct consequences on water quality and incidence of cyanobacterial blooms in the Jacarepagua Lagoon Complex (JLC). The present study combines data aiming to evaluate water quality in Jacarepagua Lagoon (JL) from monitoring of physical variables (pH, water transparency, temperature), chemical variables (salinity, dissolved oxygen, chlorophyll), the planktonic community, and the concentration of microcystins in fish from the region. The data herein presented were divided into three periods according to seasonal cycles: PI (aug/96 to sep/97), PII (jan/99 to nov/99), and PIII (feb/07 to jan/08). Dominance by cyanobacteria characterized most of the study period, interspersed with sudden peaks (e.g. during PII and PIII) of high diversity of phytoplankton. Phytoplanktonic peaks were represented by Chlorophyta, diatoms, Prasinophyta and Criptophyta. Interestingly, the events observed in 1999 repeated almost 10 years later, suggesting roughly seasonal community structure dynamism in the JLC. Disappearance of the bloom coincided with the lowest recorded water temperatures, suggesting that temperature is an important factor in the observed dynamics. The JL had a high abundance of zooplankton, yet species diversity was relatively low. Concentrations of microcystins found in muscles of fish from JL often contained values above the levels recommended by OMS for human consumption.

Relationship between zooplankton abundance and the early marine life history of juvenile chum salmon Oncorhynchus keta in eastern Hokkaido, Japan

Interannual variations in abundance, timing of outmigration from rivers, growth rate and condition of juvenile chum salmon (Oncorhynchus keta) were studied in the Nemuro Strait (eastern Hokkaido, Japan) during 1999–2002 to establish a possible relationship to zooplankton abundance. The otolith microstructure of juveniles was examined each year in late June to determine their time and size at sea entry (i.e., outmigration), and to estimate the early marine growth rates. Salmon outmigration peaked in mid- or late May, which coincided, in three of the four study years, with the peak release of juveniles into rivers within the study area. Abundance, growth rate and condition of fish were higher in 2001, when—compared to other years—smaller fish experienced higher growth rates, coinciding with greater zooplankton abundance for that year. Our results suggest that high zooplankton abundance positively influenced juvenile chum salmon growth and the condition of the fish during their early marine life despite their small size at sea entry.