High Phytoplankton Productivity Research Articles

Enhanced primary productivity and magnetotactic bacterial production in response to middle Eocene warming in the Neo-Tethys Ocean

Earth's climate experienced a warming event known as the Middle Eocene Climatic Optimum (MECO) at ~40Ma, which was an abrupt reversal of a long-term Eocene cooling trend. This event is characterized in the deep Southern, Atlantic, Pacific and Indian Oceans by a distinct negative δ18O excursion over 500kyr. We report results of high-resolution paleontological, geochemical, and rock magnetic investigations of the Neo-Tethyan Monte Cagnero (MCA) section (northeastern Apennines, Italy), which can be correlated on the basis of magneto- and biostratigraphic results to the MECO event recorded in deep-sea sections. In the MCA section, an interval with a relative increase in eutrophic nannofossil taxa (and decreased abundances of oligotrophic taxa) spans the culmination of the MECO warming and its aftermath and coincides with a positive carbon isotope excursion, and a peak in magnetite and hematite/goethite concentration. The magnetite peak reflects the appearance of putative magnetofossils, while the hematite/goethite apex is attributed to an enhanced detrital mineral contribution, likely as aeolian dust transported from the continent adjacent to the Neo-Tethys Ocean during a drier, more seasonal climate during the peak MECO warming. Based on our new geochemical, paleontological and magnetic records, the MECO warming peak and its immediate aftermath are interpreted as a period of high primary productivity. Sea-surface iron fertilization is inferred to have stimulated high phytoplankton productivity, increasing organic carbon export to the seafloor and promoting enhanced biomineralization of magnetotactic bacteria, which are preserved as putative magnetofossils during the warmest periods of the MECO event in the MCA section. Together with previous studies, our work reinforces the connection between hyperthermal climatic events and the occurrence (or increased abundance) of putative magnetofossils in the sedimentary record.

Population biology of the crab Armases angustipes (Crustacea, Decapoda, Sesarmidae) at Brazilian tropical coast

The semi terrestrial crabs are important elements of the fauna of coastal regions. The aim of this study was to analyze the population structure of Armases angustipes (Dana, 1852) at estuaries of the Ariquindá River, considered a non impacted area, and Mamucabas River, considered a few impacted area, on the south coast of state of Pernambuco, Brazil. The species occurred in all months of the year. The number of individuals per month varied, being higher in the months of transition between the seasons. This is probably due to significant seasonal variations of air and burrow temperature and burrow salinity. There was no sexual dimorphism in size of A. angustipes in the mangrove of Ariquindá River, but males were larger than females in the mangrove of Mamucabas River. In both estuaries, the sex ratio did not differ from Mendelian proportion, but showed a deviation for females. The analysis of temporal variation in sex ratio showed significant differences in some months of the year. These variations are due to cyclical events that act distinctly on each sex. In both estuaries, size classes of carapace width were equally represented by both sexes. The ovigerous females of A. angustipes occurred only in some months of the year, especially in summer, in both estuaries. Probably the high phytoplankton productivity observed in summer favors the reproductive activity, since these algae serve as food for the larvae. Specimens of the population of Rio Ariquindá are largest and wider than those of Mamucabas River. This fact, associated with the low abundance of crabs and the lower frequency of ovigerous females observed in Mamucabas River, is an indication that this population may be influenced by the environmental impacts that this estuary has received.

Seasonal hypoxia and its potential forming mechanisms in the Mirs Bay, the northern South China Sea

Hypoxia often occurs in the coastal waters of China. In the present study, data obtained from monthly cruises in the period 1998–2010 were used for analyzing temporal and spatial distributions of hypoxic bottom-water (BW) in the Mirs Bay, the northern South China Sea (NSCS). Also, potential forming mechanisms of the hypoxia were studied and depletion of the dissolved oxygen (DO) in the BW was quantitatively determined. The results showed that the BW hypoxia occurred each year in 10 years and mainly appeared from July to September in the bay within the 13-year study period. During summertime, strong density stratification formed due to both the T increase and S decrease in the surface-water in the bay. The coastal continental shelf BW had continuously intruded into and stably resided in the bay for months under influence of the NSCS southwestern monsoon. Quick biogeochemical cycles of nitrogen and phosphorus supported high phytoplankton productivity in the bay and then resulted in lots of particulate organic matter (POM) continuously to sink to the bottom. Degradation of the detritus POM, in which most was the autochthonous, resulted in DO depletion in the BW, which was estimated at about 3.6mgL−1 in the inner Tolo Harbour and 2.9mgL−1 in the main zone of the bay while the hypoxia events occurred.

Unveiling abundance and distribution of planktonic Bacteria and Archaea in a polynya in Amundsen Sea, Antarctica

Polynyas, areas of open water surrounded by sea ice, are sites of intense primary production and ecological hotspots in the Antarctic Ocean. This study determined the spatial variation in communities of prokaryotes in a polynya in the Amundsen Sea using 454 pyrosequencing technology, and the results were compared with biotic and abiotic environmental factors. The bacterial abundance was correlated with that of phytoplankton, Phaeocystis spp. and diatoms. A cluster analysis indicated that the bacterial communities in the surface waters of the polynya were distinct from those under the sea ice. Overall, two bacterial clades, Polaribacter (20-64%) and uncultivated Oceanospirillaceae (7-34%), dominated the surface water in the polynya while the Pelagibacter clade was abundant at all depths (7-42%). The archaeal communities were not as diverse as the bacterial communities in the polynya, and marine group I was dominant (> 80%). Canonical correspondence analysis indicated that the oceanographic properties facilitated the development of distinct prokaryotic assemblages in the polynya. This analysis of the diversity and composition of the psychrophilic prokaryotes associated with high phytoplankton production provides new insights into the roles of prokaryotes in biogeochemical cycles in high-latitude polynyas.

A biogeochemical model of phytoplankton productivity in an urban estuary: The importance of ammonium and freshwater flow

Increased discharge of ammonium (NH4) to the San Francisco Estuary (SFE), largely in treated domestic sewage effluent, has been linked to chronically food-limited conditions and to reduced fish abundance. Elevated chlorophyll concentrations at phytoplankton bloom levels are rarely observed if the ambient NH4 concentrations are above 4μmolL−1—the NH4 paradox. In both field samples and water held in enclosures for one week, an inverse relation was observed between NH4 concentrations and nitrate (NO3) uptake by phytoplankton, likely a result of inhibition of NO3 uptake by NH4. A simple model was constructed to examine the interaction between NH4 and NO3 inputs to the estuary, with varying freshwater river flow (hereafter termed flow) conditions. Sensitivity analyses were made and initial model parameters taken from an existing oceanic biogeochemistry model. Experiments were made with the model, and showed that initial NH4 concentrations largely controlled the length of time to peak NO3 uptake and NO3 exhaustion. The model parameters were then tuned using observations from a set of enclosure experiments, and validated with results from a series of independent enclosure experiments with a variety of initial conditions. The model was run in three flow modes: (1) with no (zero) flow, (2) with flow, a fully mixed water column and a uniform light field, and (3) with flow, a fully mixed water column but with light attenuation and depth integrated values of N uptake. In the zero flow mode the model simulated enclosure experiments and when compared with enclosure results indicated the basic NH4–NO3 interactions to be correctly represented in the model. In the modes with flow, the model simulations reproduced a sharp transition from high phytoplankton productivity using both NO3 and NH4 to low productivity using only NH4, simulating the historical effects of increasing NH4 inputs to the SFE. With vertical integration to incorporate effects of irradiance, sharp boundaries at specific combinations of varying flow and NH4 inputs were observed. The model could be embedded into three dimensional models of the SFE/Delta currently being implemented for management purposes such as regulating estuarine nutrients as required by the State of California and evaluating the effects of water management decisions on salmon and protected species of fish.

The influence of diurnal winds on phytoplankton dynamics in a coastal upwelling system off southwestern Africa

At a coastal upwelling zone near 30°S latitude, diurnal wind variability forced energetic inertial current oscillations (>0.5ms−1) that materially influenced phytoplankton distribution and productivity. The diurnal–inertial band resonance found at this latitude in the Benguela upwelling system allowed rapid, efficient transfer of energy from counterclockwise rotating winds into anticyclonic currents upon the onset of the transition from relaxation to upwelling conditions. These inertial band oscillations caused regular pycnocline outcropping at the surface and the vertical advection of nutrient-rich waters in the coastal zone. Vertical pycnocline outcropping was coincident with the vertical redistribution of chlorophyll a fluorescence from a subsurface maximum to entrainment into the surface mixed layer, in effect turning vertical phytoplankton gradients into horizontal ones. The shear caused by the vertical structure of the inertial oscillations during (and after) the onset of wind forcing was intense enough to erode the strong stratification established during a prior relaxation period, according to Richardson number and strain analyses. This diapycnal mixing also had the consequence of mixing heat and chlorophyll downwards and nutrient-rich water upwards, such that the surface nitrate concentration became non-zero. Chlorophyll concentrations thereafter increased in what qualitatively appeared to be a phytoplankton bloom. This diurnal–inertial resonance-driven mechanism for mixing-driven nutrient flux, embedded within the low-frequency advective vertical flux forced by Ekman dynamics, enhanced the efficiency of wind forcing to produce high phytoplankton productivity, and is likely to be of first-order importance in bloom dynamics in the study area (including harmful algal blooms). Our results argue that, in general, high-frequency physical dynamics should be considered when studying the bottom-up forcing of algal blooms and red tide events.

Occurrences of dissolved trace metals (Cu, Cd, and Mn) in the Pearl River Estuary (China), a large river-groundwater-estuary system

This study for the first time examined dissolved metals (Cu, Cd, and Mn) together with dissolved oxygen and carbonate system in the whole Pearl River Estuary system, from the upper rivers to the groundwater discharges until the estuarine zone, and explored their potential impacts in the adjacent northern South China Sea (SCS) during May–August 2009. This river-groundwater-estuary system was generally characterized by low dissolved metal levels as a whole, whilst subject to severe perturbations locally. In particular, higher dissolved Cu and Cd occurred in the North River (as high as 60nmol/L of Cu and 0.99nmol/L of Cd), as a result of an anthropogenic source from mining activities there. Dissolved Cu levels were elevated in the upper estuary near the city of Guangzhou (Cu: ∼40nmol/L), which could be attributable to sewage and industrial effluent discharges there. Elevated dissolved metal levels (Cu: ∼20–40nmol/L; Cd: ∼0.2–0.8nmol/L) also occurred in the groundwaters and parts of the middle and lower estuaries, which could be attributable to a series of geochemical reactions, e.g., chloride-induced desorption from the suspended sediments, oxidation of metal sulfides, and the partial dissolution of minerals. The high river discharge during our sampling period (May–August 2009) significantly diluted anthropogenic signals in the estuarine mixing zone. Of particular note was the high river discharge (which may reach 18.5 times as high as in the dry season) that transported anthropogenic signals (as indicated by dissolved Cu and Cd) into the adjacent shelf waters of the northern SCS, and might have led to the usually high phytoplankton productivity there (chlorophyll-a value >10μg/L).

Iron from melting glaciers fuels phytoplankton blooms in the Amundsen Sea (Southern Ocean): Phytoplankton characteristics and productivity

The phytoplankton community composition and productivity in waters of the Amundsen Sea and surrounding sea ice zone were characterized with respect to iron (Fe) input from melting glaciers. High Fe input from glaciers such as the Pine Island Glacier, and the Dotson and Crosson ice shelves resulted in dense phytoplankton blooms in surface waters of Pine Island Bay, Pine Island Polynya, and Amundsen Polynya. Phytoplankton biomass distribution was the opposite of the distribution of dissolved Fe (DFe), confirming the uptake of glacial DFe in surface waters by phytoplankton. Phytoplankton biomass in the polynyas ranged from 0.6 to 14μgChl aL−1, with lower biomass at glacier sites where strong upwelling of Modified Circumpolar Deep Water from beneath glacier tongues was observed. Phytoplankton blooms in the polynyas were dominated by the haptophyte Phaeocystis antarctica, whereas the phytoplankton community in the sea ice zone was a mix of P. antarctica and diatoms, resembling the species distribution in the Ross Sea. Water column productivity based on photosynthesis versus irradiance characteristics averaged 3.00gCm−2d−1 in polynya sites, which was approximately twice as high as in the sea ice zone. The highest water column productivity was observed in the Pine Island Polynya, where both thermally and salinity stratified waters resulted in a shallow surface mixed layer with high phytoplankton biomass. In contrast, new production based on NO3 uptake was similar between different polynya sites, where a deeper UML in the weakly, thermally stratified Pine Island Bay resulted in deeper NO3 removal, thereby offsetting the lower productivity at the surface. These are the first in situ observations that confirm satellite observations of high phytoplankton biomass and productivity in the Amundsen Sea. Moreover, the high phytoplankton productivity as a result of glacial input of DFe is the first evidence that melting glaciers have the potential to increase phytoplankton productivity and thereby CO2 uptake, resulting in a small negative feedback to anthropogenic CO2 emissions.

Influence of environmental factors on the growth of the juvenile, maturing juvenile, and adult tropical scallop, Euvola ziczac (Pteroida: Pectinidae), in suspended culture conditions

We carried out growth trials on three size groups of the scallop, Euvola ziczac, during two short-term (34-36 days) periods at 8, 21, and 34 m depth in Cariaco Gulf, Venezuela, in order to evaluate the effect of environmental factors on growth. Growth was greater in juveniles (initial size: 20-22 mm shell length) than in maturing juveniles (30-40 mm) and adults (70-75 mm). Somatic tissue growth was more than two-fold greater in juveniles than in maturing individuals. Adult scallops showed losses of tissue mass. The first period (December-January) covered the transition from a stratified water column to upwelling conditions, with initial high temperatures and low phytoplankton biomass followed by lower temperatures and greater phytoplankton biomass. The second period (February-March) consisted of upwelling, characterized by low temperatures and high phytoplankton production. The greater growth of juvenile and maturing scallops during the second period, particularly at 8 m depth, was associated with the greater availability of phytoplankton, related to coastal upwelling. The first development of gonads in maturing scallops only occurred in the second period, associated with food availability, and the degree of development was correlated with the depth. Our growth trials, which were too short to permit the negative impact of the development of fouling, showed that the growth of E. ziczac was enhanced in the presence of abundant phytoplankton biomass.

Mapping the pollutants in surface riverine flood plume waters in the Great Barrier Reef, Australia

The extent of flood plume water over a 10year period was mapped using quasi-true colour imagery and used to calculate long-term frequency of occurrence of the plumes. The proportional contribution of riverine loads of dissolved inorganic nitrogen, total suspended sediments and Photosystem-II herbicides from each catchment was used to scale the surface exposure maps for each pollutant. A classification procedure was also applied to satellite imagery (only Wet Tropics region) during 11 flood events (2000–2010) through processing of level-2 ocean colour products to discriminate the changing characteristics across three water types: “primary plume water”, characterised by high TSS values; “secondary plume water”, characterised by high phytoplankton production as measured by elevated chlorophyll-a (chl-a), and “tertiary plume water”, characterised by elevated coloured dissolved and detrital matter (CDOM+D). This classification is a first step to characterise flood plumes.

In situ effective clearance rate measurement of mangrove oysters (Crassostrea rhizophorae) in a tropical estuary in Brazil

Abstract Anthropogenic nutrient enrichment in estuaries induces high phytoplankton production, contributing to coastal eutrophication. Abundant natural banks of filter feeders, such as bivalves, in downstream areas may contribute to reducing symptoms of eutrophication by decreasing phytoplankton biomass and amount of material subjected to microbial regeneration. The current concern is to what extent bivalves can control water quality and how environmental parameters can influence the filtration process and vice versa. In the present study Crassostrea rhizophorae (Guilding, 1818) grazing ability on suspended particles in their natural environment was determined in situ, using the biodeposition method and uniquely constructed sediment traps. Additionally the effect of body size on effective clearance rate (ECR) was examined using three different size groups. The experiment was conducted in the Piraque-acu/Piraque-mirim estuary system, (Aracruz, ES, Brazil) during the second week of June 2012 (dry season). Environmental parameters were measured together with total particulate matter (TPM, mg L-1) and chlorophyll a analysis (CHL, μg L-1) at the beginning and at the end of the experiment. Average values recorded for TPM and CHL were 5.79 mg L-1 and 2.55 μg L-1 respectively with very high organic seston fraction (80%). The reported effective clearance rate (ECR, in litres per hour) was 17.99 L h-1g-1 dry weight (DW), one of the highest reported in literature and can be associated with a high detritus content and different feeding strategies in comparison to bivalves residing in temperate environments. Weight and length (height) relationship were closely correlated (r = 0.73) however, clearance rate (ECR) standardized to 1 g dry tissue weight did not vary significantly among different size classes. High ECR at high particulate organic matter (POM, %) supports the belief that bivalves can exhibit ECR flexibility according to food quality.

Carbon dynamics and community production in the Mississippi River plume

Dissolved inorganic carbon (DIC), total alkalinity (TAlk), pH, and dissolved oxygen (DO) were determined in the Mississippi River plume during five cruises conducted in the spring, summer, and fall. In contrast to many other large rivers, both DIC and TAlk were higher in river water than in seawater. Substantial losses of DIC, relative to TAlk, occurred within the plume, particularly at intermediate salinities. DIC removal was accompanied by high DO, high pH, and nutrient depletion, and was attributed to high phytoplankton production. As a result, the carbonate saturation in the plume became much higher than in ocean and river waters. A mixing model was used to determine DIC removal. We provide evidence that the use of a two—end‐member (river and ocean) mixing model was valid during late summer and fall (low discharge period). However, for other periods we used salinity and TAlk to delineate a mixing model that included two river end members and an ocean end member. Net community production rates in the plume, estimated using a box model, peaked in the summer and were among the highest reported to date for large river plumes. In the summer and fall, biological production in the river plume consumed a majority of the available nutrients, whereas during the spring only a small fraction of the available nutrients were consumed in the plume. Biological production was the dominant process influencing pH and carbonate saturation state along the river—ocean gradient, whereas physicochemical dynamics of mixing played an important role in controlling the TAlk and DIC distributions of this large river plume.

Influence of environmental factors on the dynamics of macrobenthic crustaceans on soft-bottoms of the Ebro Delta continental shelf (northwestern Mediterranean)

Short-term temporal variability in infaunal crustacean communities was evaluated against environmental variability. The area of study was located at two stations at 45 and 60 m depth under the influence of the Ebro River. Differences in the relative abundance of crustacean species between sites might be related to the distance from the river, with higher organic matter supply and finer mud content near the river. There was a marked seasonal variability linked to high phytoplankton production in spring, which supplied organic matter to the benthos, inducing higher crustacean abundance. In late summer there was a reduction in the infaunal crustacean abundance and species richness that could have been caused by two factors: the establishment of the thermocline, which could limit the availability of organic matter to the seabed, and the high water temperatures, which caused the production of phytoplankton exudates and accumulation of mucilaginous aggregates over the seabed. The 45-m site was under the influence of otter-trawl fishing and precisely in this area the seasonal variability was not observed, probably masked by the effects of trawling impact.

Phosphate geochemistry, mineralization processes, and Thioploca distribution in shelf sediments off central Chile

Sediments underlying the major costal upwelling systems of the world oceans are hot-spots of modern formation of hydroxyapatites, often associated with benthic communities of large, nitrate-accumulating sulfur bacteria. We studied the association between phosphate release, organic phosphorus mineralization, and occurrence of dense communities of the filamentous sulfur bacteria, Thioploca spp., on the continental shelf off central Chile during the austral summer when high phytoplankton productivity and anoxic bottom water prevailed. Freshly deposited phytodetritus stimulated extremely high sulfate reduction rates, which supported a large Thioploca community of up to 100 g biomass per m 2. Effective bacterial sulfide uptake kept the sulfide concentration low, which enabled the accumulation of free iron, thus demonstrating intensive iron reduction concurrent with sulfate reduction. Phosphate released to the pore water reached 100–300 μM peak concentrations within the uppermost 0–5 cm and phosphate was lost to the overlying anoxic water column. The large phosphate release was not directly related to the presence of Thioploca but was rather the result of a high deposition and mineralization rate of fresh organic detritus. Although the pore water was super–saturated with respect to hydroxyapatite, this mineral was only a minor P-component in the sediment. Most solid-phase phosphate was bound to iron.

Space-time variability of phytoplankton structure and diversity in the north-western part of the Arabian Gulf (Kuwait)

Studies of the phytoplankton community were conducted in the north-western Arabian Gulf in 2005 and 2006. Seven stations throughout Kuwait’s waters were sampled. The influence of nutrient-rich freshwaters from the Shatt al-Arab resulted in high phytoplankton productivity characterized by high species diversity with a strong dominance of diatoms, especially in northern Kuwait. Phytoplankton species richness gradually increased from north to south. Spatial distribution of both total abundance and biomass of phytoplankton indicated significant differences in species structure and size spectrum of the microalgae. The analysis of the temporal and spatial phytoplankton variability (distribution of total abundance and biomass, similarity of species compositions and local community structure) indicated that Kuwait’s northern waters differed from areas further south in terms of phytoplankton structure and temporal and spatial variability. Environmental heterogeneity is mainly attributed to the influence of the Shatt al-Arab system, which affects the temporal and spatial variability of the phytoplankton community.

Changes of water level in the Eemian palaeolake at Imbramowice (SW Poland) based on isotopic and cladoceran data

Isotopic and cladoceran investigations of Eemian (MIS 5e) lake sediments from Imbramowice, SW Poland, allow us to reconstruct the environmental conditions, especially changes of water level and trophic status, during the early and middle Eemian Interglaciation. We analyzed the sediments from 6.5 to 11.0 m depth in a core provided by Mamakowa (1989). The upper 6.5 m had insufficient carbonates and cladoceran contents for analyses. The analyzed section consists of sandy and organic silts at the bottom, followed by gyttja characterized by increasing CaCO 3 content. Measured δ 18O values oscillate from ca. – 9 to – 4‰ and δ 13C from – 3.5 to above + 6‰. Based on stable isotope analyses of carbonates, we define and characterize eight isotopic horizons (Is). We identify 26 taxa of subfossil Cladocera and seven zones (CLZ) of faunal development. Probably the greatest depth of the lake occurred with pollen zone E2; shallowing then took place. During pollen zones E2-E3, gradual warming is observed and expressed through a positive trend in both δ 18O and δ 13C values. Pollen zone E4 is characterized by frequent changes of water level. During the Eemian Interglaciation, excluding the initial phase of lake evolution, the lake was meso-eutrophic and eutrophic with high phytoplankton productivity.

Phytoplankton production after the collapse of the Larsen A Ice Shelf, Antarctica

Part of the Larsen A Ice Shelf (64°15′S to 74°15′S) collapsed during January 1995. A first oceanographic and biological data set from the newly free waters was obtained during December 1996. Typical shelf waters with temperatures near and below the freezing point were found. A nutrient-rich water mass (max: PO4 3− 1.80 μmol L−1 and NO3 − 27.64 μmol L−1) was found between 70 and 200 m depth. Chlorophyll-a (Chl-a) values (max 14.24 μg L−1) were high; surface oxygen saturation ranged between 86 and 148%. Diatoms of the genera Nitzschia and Navicula and the prymnesiophyte Phaeocystis sp. were the most abundant taxa found. Mean daily primary production (Pc) estimated from nutrient consumption was 14.80 ± 0.17 mgC m−3 day−1. Pc was significantly correlated with total diatom abundance and Chl-a. Calculated ΔpCO2 (difference of the CO2 partial pressure between surface seawater and the atmosphere) was –30.5 μatm, which could have contributed to a net CO2 flux from the atmosphere to the sea and suggests the area has been a CO2 sink during the studied period. High phytoplankton biomass and production values were found in this freshly open area, suggesting its importance for biological CO2 pumping.

Satellite observations of main oceanographic processes to identify ecological associations in the Northern Arabian Sea for fishery resources exploration

Ecological associations are the inter-relationship between the species and their environment. Oceanographic processes like upwelling events and formation of eddies, rings, and fronts have been monitored using National Oceanic and Atmospheric Administration Advanced Very High Resolution (NOAA AVHRR) and Indian Remote Sensing Satellite-P4-Ocean Colour Monitor (IRS-OCM) data. Sea Surface Temperature (SST) and chlorophyll concentration (CC) images were derived from AVHRR and OCM, respectively. Upwelling event was monitored using AVHRR-SST by detecting the differences in surface water temperature. The formation of eddies, rings, cyclonic eddies, and anti-cyclonic eddies and their biological responses were studied using CC. Eddies and rings were found with high phytoplankton production in the form of bloom, which provide grazing ground for fishes. The anti-cyclonic eddies were found with very low CC, indicating the biological deserts in the ocean. The impacts of these processes on fish catch were studied using fishing operations data procured from Fishery Survey of India. In this paper, the occurrence of different oceanographic processes, their persistence, and relevance with catch statistics of fishery resources in the study area are discussed. The study explains the potentials of satellite remote sensing to establish the habitat linkage between oceanographic processes and fishery resources.

Effect of temperature and phytoplankton concentration of Partitioned Aquaculture System water on freshwater mussel filtration

AbstractThe freshwater mussel Elliptio complanata wasprovided green algal-dominated water from a Parti-tioned Aquaculture System (PAS) over a range ofwater temperatures (6.1^32.41C) and suspendedparticulate organic carbon (POC) concentrations(o1^32.2mgCL 1 ) to determine ¢ltration rates asmgPOCkg 1 wet tissue weighth . The lowest ¢l-tration rates were observed at lowest temperaturesand POC concentrations while thehighest rates wereat intermediate temperatures and the highest POClevels. The predicted ¢ltration rate (PFR) in responseto water temperature and POC concentrations wasas follows: lnPFR51.4352 10.1192 POC 10.1399T 0.0001 T 3 . Within the experimental conditions,PFRs at any POC concentration increased withincreased water temperature to a peak at 221Candthen decreased. The maximum PFR occurredat 22 1Cand32mgCL 1 and the minimum PFRat 7 1Cand1mgCL 1 . A model to describe themussel ¢ltration rate responses to PAS waterconditions involves both water temperature and POCconcentration.Keywords: ¢ltration rate, freshwater mussel, PAS,culturesystemIntroductionA Partitioned Aquaculture System (PAS) separates aculture pond into four distinct components (paddle-wheels, algal basin, ¢lter-feeder area and culturespeciesarea)linkedbyahomogeneouswatervelocity¢eld (Brune, Schwartz, Eversole, Collier & Schwedler2004). Paddlewheels provide watercurrent, nutrientmixing,uniformsunlightexposuretophytoplanktonandcontinuous£owoverthealgalbasin,¢lterfeederand cultured species areas. Phytoplankton inthe al-galbasin(95%ofthePASarea)useinorganic¢shme-tabolic wastes (nutrients) to sustain high primaryproductivity levels. Feeding rates and ¢sh carryingcapacityof thePASisaboutthreeto ¢vetimesthatofconventional cat¢sh culture ponds because of sus-tained high phytoplanktonproductivity (Brune etal.2004).Filter-feedingorganisms,byharvestingphyto-plankton, reduce cell age and stabilize a standingcrop of faster-growing phytoplankton cells at re-duced respiration rates and increased oxygen pro-ductionper watervolume(Bruneetal.2004).Someofthetermsusedinliteraturetoexpress¢ltra-tion activity of suspension feeders include clearancerate, pumping rate, ¢ltration rate, ingestion rate, up-take rate, and retention rate (see, e.g. Foster-Smith1975; Walz 1978, Winter 1978; Riisgrd 2001a). Theterm ¢ltration rate inthis studyand inthis paper re-fers strictly to the amount of suspended phytoplank-ton(seston)removedfromthewatercolumnperunittimeandincludesboththose¢lteredparticlesconso-lidated in pseudofaeces and those consumed, and isidentical to the terms uptake rate and retention rateof Foster-Smith (1975) andWalz (1978).The role of a¢lterfeederinstabilizingalgalstandingcropbiomassin PAS water is more appropriately estimated usingthis de¢nition of ¢ltration rate than measures esti-matingtheamountofwater¢lteredoringestionrate.

Production of lower-trophic organisms during incubation of unaltered deep-sea water

Incubation of unaltered deep-sea water and grazing experiment of nano- and micro- protozooplankton during incubation of deep-sea water were carried out to quantitatively characterize the planktonic structures of lower-trophic organisms and clarify the trophic pathways and controlling mechanisms involved. Phytoplankton biomass increased to 637 mg as carbon weight in a 500-l tank on Day 7 and was dominant in the planktonic structure of lower-trophic organisms. Nitrates in the incubation water was depleted after Day 7 and phytoplankton biomass decreased rapidly. On the other hand, bacteria, heterotrophic nano-flagellates and ciliates increased toward the end of incubation and were dominant in the later days of incubation. In grazing experiments on microbial organisms, bacterivory is more important for the carbon pathway in microbial food webs than herbivory when phytoplankton biomass is less than that of bacteria (low P/B conditions), while herbivory is more important than bacterivory when phytoplankton biomass is more than that of bacteria (high P/B conditions). Deep-sea water exhibited high phytoplankton productivity due to inherent high nutrients values. After depletion of nutrients, phytoplankton decreased (due also to enhanced nano- and micro-zooplankton grazing) and microbial organisms dominated. Thus, nutrients in the incubation water control the planktonic structure of lower-trophic organisms.