Plankton

The taxonomy and distribution of halocyprid ostracods from the Arabian Sea Region is reported, based upon samples collected in the Northwestern Indian Ocean within the framework of the Netherlands Indian Ocean Program (NIOP: 1992-1993), the U.S. Joint Global Ocean Flux Study (U.S. JGOFS: 1994–1996), and the U.S. Global Ocean Ecosystem Dynamics program (U.S. GLOBEC: 1995). Forty-one species from the following genera belonging to the family Halocyprididae are
described, illustrated, and representative photographs are presented: Archiconchoecia, Alacia, Conchoecetta, Conchoecia, Conchoecilla, Conchoecissa, Discoconchoecia, Loricoecia, Mikroconchoecia, Orthoconchoecia, Paraconchoecia, Paramollicia, Platyconchoecia, Porroecia, Proceroecia,
Pseudoconchoecia, Clausoecia, Kyrtoecia, Nasoecia and Euconchoecia. For fourteen species, members of the genera Macroconchoecia, Mollicia, Paraconchoecia, Metaconchoecia, Mülleroecia, Fellia, Halocypria and Halocypris, only carapace outlines are presented. Keys to the subfamilies, tribes, genera and species, and patterns of horizontal and vertical distribution of each described species in the Arabian Sea Region are also given. The data on occurrence of halocyprid species at each of the stations during the investigation period and the depth ranges of halocyprid species found in the analyzed material but not described in the present book are listed in appendices.

Aquatic coastal systems are affected by high fluctuations in salinity and the zooplankton may rely on dispersal or dormancy to recolonise these environments. Here, we analysed the long-term dynamics of the zooplankton community over 6 years during large salinity fluctuations in a coastal lagoon (Garças Lagoon, Brazil) and the effect of salinity on the hatching patterns of the resting egg bank. We hypothesised that salinity is the main driving factor of the zooplankton community structure, and that increases in salinity reduce the species richness and the abundance of hatchlings. Multiple regression analysis showed that salinity was associated negatively with species richness in the open water, whereas total phosphorus and chlorophyll-a concentrations were negatively and positively related to abundance respectively. Redundancy analysis demonstrated that temporally structured environmental variables (total phosphorus and salinity) were important for zooplankton composition. Periods of...

Spatial and seasonal egg production rates (Er) and egg hatching success in the copepods Calanus finmarchicus and Calanus helgolandicus were measured in the North Sea from March to September. Food availability was monitored by chlorophyll and protist concentrations and three size fractions of seston fatty acids. Seasonal and spatial distribution and production differed between the species. Calanus finmarchicus was found only offshore of the 50-m isobath, with decreasing Er (37–28 eggs female−1 day−1) from March to July. Calanus helgolandicus had two abundance peaks, in spring and autumn, with a low in May during which time the highest Er were observed (38 eggs female−1 day−1). At other times, Er in C. helgolandicus remained lower than in C. finmarchicus (∼20 eggs female−1 day−1). Normalized Er (En) in both C. finmarchicus and C. helgolandicus were positively related to ciliate biomass while only negative relationships were found for all other variables measured. Hatching success in b...

Comau Fjord is a stratified Chilean Patagonian Fjord characterized by a shallow brackish surface layer and a >400 m layer of aragonite-depleted subsurface waters. Despite the energetic burden of low aragonite saturation levels to calcification, Comau Fjord harbours dense populations of cold-water corals (CWC). While this paradox has been attributed to a rich supply of zooplankton, supporting abundance and biomass data are so far lacking. In this study, we investigated the seasonal and diel changes
of the zooplankton community over the entire water column. We used a Nansen net (100 mm mesh) to take stratified vertical hauls between the surface and the bottom (0-50-100-200-300-400-450 m). Samples were scanned with a ZooScan, and abundance, biovolume and biomass were determined for 41 taxa identified on the web-based platform EcoTaxa 2.0. Zooplankton biomass was the highest in summer (209 g dry massm􀀀2) and the lowest in winter (61 g dry massm􀀀2). Abundance, however, peaked in spring, suggesting a close correspondence between reproduction and phytoplankton spring blooms (Chl a max. 50.86 mgm􀀀3, 3mdepth). Overall, copepods were the most important group of the total zooplankton community, both in abundance (6481%) and biovolume (2070%) followed by mysids and chaetognaths (in terms of biovolume
and biomass), and nauplii and Appendicularia (in terms of abundance). Throughout the year, diel changes in the vertical distribution of biomass were found with a daytime maximum in the 100200 m depth layer and a nighttime maximum in surface waters (050 m), associated with the diel vertical migration of the calanoid copepod family Metridinidae. Diel differences in integrated zooplankton abundance, biovolume and
biomass were probably due to a high zooplankton patchiness driven by biological processes (e.g., diel vertical migration or predation avoidance), and oceanographic processes (estuarine circulation, tidal mixing or water column stratification). Those factors are considered to be the main drivers of the zooplankton vertical distribution in Comau Fjord.

This study investigated the behaviour of Pomacea bridgesii, describing the daily activity, substrate selection and the influence of the flood regime in the Amazon, the species’ native habitat. The present study described the daily activity and substrate selection, and evaluated the activity adaptations of the gastropods in a simulated flood-pulse regime. Gastropods were collected in Amazonas, Brazil, in June 2013. Assessments of the daily behaviour, substrate selection, and flood-pulse simulation were made in experimental water tanks. The snails were observed hourly for 48h, and their behaviour recorded on an ethogram. The snails were more active during the night, when up to 80% of them moved about. In general, during both day and night, the gastropods used the pebble substrate most often. Comparing the day periods, a significant proportion of the individuals that were using the pebbles moved to other substrates (t=5; d.f.=2; P=0.03). The interaction of the behaviour of P. bridgesii...

Due to their boom and bust population dynamics and the enormous biomasses they can attain, jellyfish and ctenophores can have a large influence on the cycling of carbon (C), nitrogen (N) and phosphorus (P). This review initially summarises the biochemical composition of jellyfish, and compares and contrasts the mechanisms by which non-zooxanthellate and zooxanthellate jellyfish acquire and recycle C, N

Identifying the respective role of environmental, landscape and management factors in explaining the patterns in community composition is an important goal in ecology. Using a set of 32 temporary ponds in northern Morocco we studied the respective importance of local (within the pond) and regional (density of ponds in landscape) factors and the impacts of different land uses on the plant species assemblages, separating pond and terrestrial species. The main hypotheses tested were that (1) species assemblages respond to both local and regional environmental factors, (2) anthropogenic pressure has a negative influence on the number of pond species, and that (3) human activities differ in their impact on pond biodiversity. The results showed that (1) local factors explain most of the variation in plant community composition, and (2) land use impacts the communities through changing local environmental conditions, leading to a loss of typical pond species. Aside from recreation, all oth...

Parasites constitute the majority of coral reef animal diversity and are believed to contribute significantly to host, community and trophic dynamics. Anilocra spp. are large conspicuous ectoparasitic isopods, making them ideal models for host–parasite studies. In the tropical western Atlantic and Caribbean, Anilocra haemuli infects the ecologically important French grunt (Haemulon flavolineatum). French grunt are trophic connectors between reef and seagrass environments, and how A. haemuli infection influences connectivity is unknown. As a first step in understanding the French grunt–A. haemuli association, we conducted reef surveys during three consecutive years to quantify the abundance and prevalence of infected fish on reef sites in the north-eastern Caribbean. We examined their correlations with fish population and aggregation size, and social affiliation. Annual infected fish abundance and prevalence per site ranged from 0–24 fish and 0–66%. Prevalence: (1) appeared autocorre...

Polychlorinated biphenyls (PCBs) were quantified in bulk seawater (3.1 ± 1.0 ngl−1, N = 3) in 1976, in plankton (2.9 ± 3.3 ng g−1 wet weight, N = 176) in 1976 and 1977 and in fish (155 ± 194 ng g−1 wet weight, N = 135) in 1977 collected from St. Georges Bay in the southern Gulf of St. Lawrence. PCB concentrations in the plankton of the entire water column varied seasonally by ten times, with the highest values occurring in spring, lowest during summer and variable levels in late fall. The lower PCB levels in the total summer community coincide with a reduced biomass in certain size fractions in the Bay rather than a decrease in PCB concentration of the plankton. PCBs were concentrated in the middle-sized fractions of the planktonic community and this is attributed to the greater biomass present in these categories. PCB concentrations in plankton were most highly correlated with their lipid content at the time of sampling. Seasonal reductions of lipid in the plankton per m3 resulted in a higher concentration of PCB per unit lipid in the remaining community. Planktonic PCB concentrations, expressed on a lipid basis, are found to be correlated with cumulative rainfall 21 d before sampling for both years combined.Adult fish were more contaminated by PCBs than either their egg or juvenile stages. Mature gaspereau, herring and smelt had higher concentrations of PCB contamination than mackerel, capelin, white hake and silversides. No difference was found between PCB contamination of the sexes of fish species analyzed. PCBs were transferred from mother to offspring in fish, but at lower levels than the level present in the parent; and the maximum accumulation from the environment occurred between immature and adult fish. The best predictors of PCB contamination in fish in St. Georges Bay are lipid content followed by size and age.PCB concentrations in plankton, normalized to lipid content, did not increase with size or trophic level. PCB concentrations in fish increased with size and on average were ten times the levels found in plankton. Marine mammals collected by other researchers in the region during the 1970s had accumulated up to several orders-of-magnitude higher concentrations than those found in fish, with a more gradual increase with size of organism. Lipid content and age or exposure period appear to be the main factors which determine PCB concentrations in the marine food chain in the southern Gulf of St. Lawrence.

The effects of fish kill and different fish stocks on the phytoplankton and zooplankton dynamics were studied in a shallow hypertrophic reservoir system. When fish stock was below 100 kg ha-1, nutrient availability was not the main limiting factor for growth of phytoplankton. Consequently top-down forces controlled phytoplankton. In the years with high fish stock (>100 kg ha-1) the bottom-up forces dominated as nutrient availability was the main limiting factor for growth of phytoplankton. We can conclude that significant water quality improvement can be achieved in the reservoir system by decreasing fish stock below 100 kg ha-1. Although clear-water phase could be stabilised temporary by macrophytes, stabilisation of good water quality requires continuous regulation of fish community. (

Lake Vela is a polymictic shallow lake exhibiting some characteristics typical of an advanced trophic state, namely, the permanently turbid water, the reduction in biodiversity, and the recurrent occurrence of Cyanobacteria blooms, which occasionally lead to large fish kills. This study was carried out in order to understand the seasonal variation of Lake Vela’s phytoplankton and cladoceran communities and their interactions under advanced eutrophic conditions. When comparing our results with general models of plankton succession observed in other temperate and tropical lakes we found some coherence between several seasonal events. Our results suggest that phytoplankton is mainly regulated by nutrients (“bottom-up” effect). However, the warm mediterranean temperatures had an important role in the phytoplankton succession, being responsible for the rapid and intense Cyanobacteria development in spring and summer. Our work also demonstrated that phytoplankton is one of the main factors responsible for the seasonal structure of the community of cladocerans, which are well related to changes in algae diversity and abundance, being the Cyanobacteria having major impact. Moreover, the occurrence of a massive Cyanobacteria bloom during the study, which induced anoxia and consequent fish kill, enhanced the structuring role that fish have on the cladoceran seasonal succession and the effects of this episode in the normal seasonal succession of plankton.

"Um den Einfluss der Form auf das Absinkverhalten von Plankton
in der Schule zu untersuchen, wird oft das Sinkenlassen von
Plastillinmodellen in Wasser vorgeschlagen. Dabei wird nicht
berucksichtigt, dass das Absinken von großen Modellen anderen ̈
hydrodynamischen Gesetzen gehorcht als bei im Mikrometerbereich liegenden realen Planktern. Um diese Versuche realitatsnaher zu gestalten, wird vorgeschlagen, viskosere Flussigkeiten als Wasser zu verwenden, beispielsweise Zuckerlosung oder Motorol.

Microstructure and acoustic profile time series were collected near Ocean Station P in the eastern subarctic North Pacific and in Saanich Inlet at the south end of Vancouver Island, British Columbia, Canada, to examine production of turbulent dissipation by swimming marine organisms. At Ocean Station P, although a number of zooplankton species are large enough to generate turbulence with Reynolds numbers Re > 1000, biomass densities are typically less than 103 individuals per cubic meter (<0.01% by volume), and turbulent kinetic energy dissipation rates ε were better correlated with 16-m vertical shear than acoustic backscatter layers. In Saanich Inlet, where krill densities are up to 104 individuals per cubic meter (0.1% by volume), no dramatic elevation of dissipation rates ε was associated with dusk and dawn vertical migrations of the acoustic backscatter layer. Dissipation rates are a factor of 2 higher [〈ε〉 = 1.4 × 10−8 W kg−1, corresponding to buoyancy Re = 〈ε〉/(νN 2) ∼ ...

A crucial moment in the history of plankton research came during the 1920s with the introduction of the notion of biomass. Biomass links the 19th century aspirations elicited by plankton as the bottom of the food chain with the technocratic dreams of the perfect metabolic loop between aquatic mass and terrestrial needs of human beings during the 20th century. This article shows that the history of plankton research can be told as succession of historically bound epistemic hopes and societal utopia. It becomes evident that plankton as an individual organism is fragile yet simultaneously unchanging and able to resist most technical interventions and notions of optimization.

Water-column mixing is known to have a decisive impact on plankton communities. The underlying mechanisms depend on the size and depth of the water body, nutrient status and the plankton community structure, and they are well understood for shallow polymictic and deep stratified lakes. Two consecutive mixing events of similar intensity under different levels of herbivory were performed in enclosures in a shallow, but periodically stratified, eutrophic lake, in order to investigate the effects of water-column mixing on bacteria abundance, phytoplankton abundance and diversity, and rotifer abundance and fecundity. When herbivory by filter-feeding zooplankton was low, water-column mixing that provoked a substantial nutrient input into the euphotic zone led to a strong net increase of bacteria and phytoplankton biomass. Phytoplankton diversity was lower in the mixed enclosures than in the undisturbed ones because of the greater contribution of a few fast-growing species. After the second mixing event, at a high biomass of filter-feeding crustaceans, the increase of phytoplankton biomass was lower than after the first mixing, and diversity remained unchanged because enhanced growth of small fast-growing phytoplankton was prevented by zooplankton grazing. Bacterial abundance did not increase after the second mixing, when cladoceran biomass was high. Changes in rotifer fecundity indicated a transmission of the phytoplankton response to the next trophic level. Our results suggest that water-column mixing in shallow eutrophic lakes with periodic stratification has a strong effect on the plankton community via enhanced nutrient availability rather than resuspension or reduced light availability. This fuels the basis of the classic and microbial food chain via enhanced phytoplankton and bacterial growth, but the effects on biomass may be damped by high levels of herbivory.

ABSTRAK Danau Mawang terletak di Kelurahan Mawang, Kecamatan Somba Opu, Kabupaten Gowa, Provinsi Sulawesi Selatan dengan dengan luas danau mencapai 111.2 Ha yang dapat dijadikan sebagai media dalam melakukan usaha dibidang budidaya perikanan yang salah satu unsur penting adalah plankton. Plankton selain sebagai dasar rantai makanan juga merupakan parameter tingkat kesuburan suatu perairan. Penelitian ini bertujuan untuk mengetahui struktur komunitas dan kelimpahan Plankton di danau Mawang sebagai parameter tingkat kesuburan suatu perairan. Hasil dari analisa struktur kelimpahan plankton didapatkan kisaran kelimpahan rata-rata plankton di danau mawang adalah 136.467 sel/liter. Berdasarkan kelimpahan plankton tersebut, perairan danau mawang termasuk dalm kategori eutrofik. Nilai indeks keanekaragaman plankton yang diperoleh adalah 0,5618. yang termasuk dalam kategori kesuburan rendah. Nilai indeks keseragaman di perairan danau mawang yakni 0,0475 yang dapat diartikan bahwa penyebaran individu setiap jenis di dalam komunitasnya relatif merata, sementara Sementara indeks dominasi memiliki nilai 0,6732 hasil perhitungan tersebut tidak mendekati 0 (nol) dan hampir mendekati 1 (satu) dimana dapat diketahui bahwa di perairan danau mawang terjadi dominasi plankton. ABSTRACT Mawang lake is located in the Village Mawang, District Somba Opu, Gowa, South Sulawesi province with an area of the lake reached 111.2 Ha which can be used as a medium of doing business in the field of aquaculture is one of the important elements is plankton. Plankton apart as the base of the food chain is also a parameter of a fertility waters. This study aims to determine the community structure and abundance of plankton in the lake Mawang as a fertility rate parameter waters. The results of the analysis of the structure of plankton abundance get a range of the average abundance of plankton in the lake Mawang is 136 467 cells / liter. Based on the abundance of plankton, the lake waters Mawang including preformance eutrophic category. Values obtained plankton diversity index is 0.5618. are included in the category of low fertility. An index value of uniformity in the waters of the lake Mawang 0.0475 which means that the spread of individuals of each species in the community is relatively evenly distributed, while While the dominance index has a value of 0.6732 results of these calculations are not close to 0 (zero) and almost close to 1 (one) where it can be seen that in the waters of the lake plankton Mawang domination.