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1.
《Marine pollution bulletin》2011,62(7-12):399-412
In order to quantify the spatial and seasonal variations of sediment oxygen consumption and nutrient fluxes, we performed a spatial survey in the south west lagoon of New Caledonia during the two major seasons (dry and wet) based on a network of 11 sampling stations. Stations were selected along two barrier reef to land transects representing most types of sediments encountered in the lagoon. Fluxes were measured using ex-situ sediment incubations and compared to sediment characteristics. Sediment oxygen consumption (SOC) varied between 500 and 2000 μmol m−2 h−1, depending on season and stations. Nutrient effluxes from sediment were highly variable with highest fluxes measured in muddy sediments near the coast. Inter-sample variability was as high as seasonal differences so that no seasonally driven temperature effect could be observed on benthic nutrient fluxes in our temperature range. Nutrient fluxes, generally directed from the sediment to the water column, varied between −5.0 and 70.0 μmol m−2 h−1 for ammonia and between −2.5 and +12.5 μmol m−2 h−1 for PO4 and NO2+3. SOC and nutrient fluxes were compared to pelagic primary production rates in order to highlight the tight coupling existing between the benthic and pelagic compartments in this shallow tropical lagoon. Under specific occasions of low pelagic productivity, oxygen sediment consumption and related carbon and nutrient fluxes could balance nearly all net primary production in the lagoon. These biogeochemical estimates point to the functional importance of sediment biogeochemistry in the lagoon of New Caledonia.  相似文献   

2.
Sediment oxygen consumption, TCO2 production and nutrient fluxes across the sediment-water interface were measured in sediments within and along a transect from four fish pens with production of milkfish (Chanos chanos) in the Bolinao area, The Philippines. The four fish pens were each representing a specific period in the production cycling. There was a positive linear relationship between the rates of sedimentation inside the fish pens and the sediment oxygen consumption indicating that the benthic processes were controlled by the input of organic matter from fish production. The nutrient fluxes were generally higher inside the fish pens, and nitrate was taken up (1.7-5.8 mmol m(-2) d(-1)) whereas ammonium (1-22 mmol m(-2) d(-1)) and phosphate (0.2-4.7 mmol m(-2) d(-1)) were released from the sediments. The sediments were enriched in organic matter with up to a factor 4 compared to outside. A mass balance for one crop of milkfish was constructed based on production data and on measured fluxes of nutrients in the fish pens to assess the loss of carbon and nutrients to the environment. There was a loss to the surroundings of carbon and nitrogen of 51-68% of the total input, whereas phosphorus was buried in the sediments inside the fish pens which acted as net sinks of phosphorus. The results obtained suggest that fish pen culture as practiced in the Bolinao area, leads to even greater impacts on benthic carbon and nutrient cycling than those found in suspended cage cultures.  相似文献   

3.
The use of pearl oysters has recently been proposed as an environmental remediation tool in coastal ecosystems. This study quantified the nitrogen, phosphorus and heavy metal content of the tissue and shell of pearl oysters harvested from a small pearl oyster farm at Port Stephens, Australia. Each tonne of pearl oyster material harvested resulted in approximately 703 g metals, 7452 g nitrogen, and 545 g phosphorus being removed from the waters of Port Stephens. Increasing current farm production of 9.8 tyr(-1) to 499 tyr(-1) would balance current nitrogen loads entering Port Stephens from a small Sewage Treatment Plant (STP) located on its southern shores. Furthermore, manipulation of harvest dates to coincide with oyster condition would likely remove substantially greater quantities of nutrients. This study demonstrates that pearl aquaculture may be used to assist in the removal of pollutants from coastal waters while producing a commercially profitable commodity.  相似文献   

4.
A two year survey of benthic primary production during periods of emersion was performed on two stations of an intertidal mudflat (a muddy-sand station and a muddy station) in the Seine Estuary (English Channel, France). The goals of this study were to investigate the seasonal variations of metabolism, to estimate daily potential primary production variation at the annual scale and to estimate the annual potential primary production of the mudflat. Primary production and respiration were estimated by in situ measurements of carbon dioxide fluxes. Chlorophyll a concentration exhibited a great variability on both locations. Gross community production ranged from ca. 0 to 77 mg C m(-2) h(-1) at the muddy-sand location and from ca. 0 to 122 mg C m(-2) h(-1) at the muddy location. Community respiration showed a seasonal trend following temperature variations (up to 28.51 mg C m(-2) h(-1) in the muddy-sand and up to 23.40 mg C m(-2) h(-1) in the mud). Daily potential primary production was calculated, according to seasonal variations of photosynthetic parameters calculated using three photosynthesis versus irradiance curves obtained for the muddy location. The annual gross community primary production was 135 g C m(-2) yr(-1), leading to a low autotrophic annual budget, considering an annual community respiration of 110 g C m(-2) yr(-1).  相似文献   

5.
Fish farms represent a growing source of anthropogenic disturbance to benthic communities, and efficient predictors of such impacts are urgently needed. We explored the effects of fish farm benthic organic and nutrient inputs on the population dynamics of a key seagrass species (Posidonia oceanica) in four Mediterranean deep meadows adjacent to sea bream and sea bass farms. We performed two annual plant censuses on permanent plots at increasing distance from farms and measured benthic sedimentation rates around plots. High shoot mortality rates were recorded near the cages, up to 20 times greater than at control sites. Recruitment rates increased in variability but could not compensate mortality, leading to rapid seagrass decline within the first 100 m from cages. Seagrass mortality increased with total sedimentation rates (K=0.55, p<0.0002), and with organic matter (K=0.50, p=0.001), total nitrogen (K=0.46, p=0.002) and total phosphorus (K=0.56, p<3.10(-5)) inputs. P. oceanica decline accelerated above a phosphorus loading threshold of 50mg m(-2)day(-1). Phosphorus benthic sedimentation rate seems a powerful predictor of seagrass mortality from fish farming. Coupling direct measurements of benthic sedimentation rates with dynamics of key benthic species is proposed as an efficient strategy to predict fish farm impacts to benthic communities.  相似文献   

6.
Atoll lagoons display a high diversity of trophic states due mainly to their specific geomorphology, and probably to their level and mode of human exploitation. We investigated the functioning of the Ahe atoll lagoon, utilized for pearl oyster farming, through estimations of photosynthetic parameters (pulse amplitude modulation fluorometry) and primary production ((13)C incorporation) measurements of the size structured phytoplankton biomass (<2μm and >2μm). Spatial and temporal scales of variability were surveyed during four seasons, over 16months, at four sites within the lagoon. While primary production (P) was dominated by the picophytoplankton, its biomass specific primary productivity (P(B)) was lower than in other atoll lagoons. The variables size fraction of the phytoplankton, water temperature, season, the interaction term station*fraction and site, explained significantly the variance of the data set using redundancy analysis. No significant trends over depth were observed in the range of 0-20m. A clear spatial pattern was found which was persistent over the seasons: south and north sites were different from the two central stations for most of the measured variables. This pattern could possibly be explained by the existence of water cells showing different water residence time within the lagoon. Photoacclimation strategies of the two size fractions differed through their light saturation coefficient (higher for picophytoplankton), but not through their maximum photosynthetic capacity (ETR(max)). Positive linear relationships between photosynthetic parameters indicated that their dynamic was independent of light availability in this ecosystem, but most probably dependent on nutrient availability and/or rapid changes in the community structure. Spatial and temporal patterns of the measured processes are then further discussed in the context of nutrient availability and the possible role of cultured oysters in nutrient recycling.  相似文献   

7.
To assess the impact of an artificial dyke in Chonsu Bay (CBD) on the organic carbon (C(org)) cycle, we measured excess (210)Pb activities, C(org) and nitrogen content in sediment cores. The C(org) oxidation rates (C(ox)) on the surface sediment and benthic nutrient fluxes were also quantified with an in situ benthic chamber. The higher excess (210)Pb inventory, C(org) and nitrogen in cores near the CBD indicated lateral transport and local, massive deposition of particulate matter due to tidal circulation altered by artificial dyke construction. The C(ox) in sediment near the CBD was about twice as high as that out of the bay, suggesting the importance of benthic remineralization of organic matter. The benthic fluxes of dissolved inorganic nitrogen and phosphate were four to six times higher than those outside the bay, corresponding to 141% and 131% respectively, of the requirements for primary production.  相似文献   

8.
Effects of suspended mussel and infaunal clam cultivation on sediment characteristics, and benthic organic and inorganic nitrogen and phosphorus fluxes were compared in a shallow coastal lagoon. The two species had different impacts on sediment features, but both created “hotspots” of nutrient fluxes with annual N and P regeneration rates being 4.9 and 13.5 (mussel) and 4.5 and 14.9 (clams) fold greater than those of unfarmed control sediments. Mussel farming also caused considerable nutrient regeneration within the water column with the mussel ropes contributing ∼25% of total inorganic N and P production and at times dominating the sediments (e.g. 95% of SRP production in summer and 45% of DIN production in winter). Such nutrient regeneration rates seriously question the proposal that suspension-feeding bivalves act as a eutrophication buffer, especially during summer when nutrient regeneration rates are maximal, but other nutrient sources (freshwater run-off and unfarmed sediments) are at their lowest.  相似文献   

9.
Fluxes of dissolved inorganic nutrients: NH4+, NO2-, NO3-, PO4(3-) and Si(OH)4 from nearshore sediments of Gazi Bay were measured in situ within mangrove, seagrass and coral reef biotopes using benthic flux bell-jar chambers of cross-sectional area 0.066 m2 and volume 0.0132 m3. The objectives were: (1) to determine the influence of benthic fluxes, fluvial discharge and seasonal variations on the nutrient budget in the Bay waters; (2) to determine the effect of tidal and spatial variations on nutrient loads in the water column and (3) to establish the relative importance of the nutrient sources with regard to total community production of the Bay. The directly measured fluxes ranged from -270 to +148 micromol NH4+-N/m2/h; -60 to +63 micromol NO2(-)-N/m2/h; -79 to +41 micromol NO3(-)-N/m2/h; -79 to +75 micromol PO4(3-)-P/m2/h and +30 to +350 micromol Si(OH)4-Si/m2/h for and respectively. It was established that benthic fluxes are the major sources of dissolved inorganic NH4+, NO2- and Si(OH)4 while fluvial sources are important for NO3- and PO4(3-) into Gazi Bay waters. Seasonal variations had an appreciable effect on the PO4(3-) fluxes, N:Si ratio, river nutrient discharge, plankton productivity and important environmental factors such as salinity and temperature. Tidal and spatial variations had no significant effect on nutrient concentrations and net fluxes within the water column. The results imply that benthic fluxes are largely responsible for the nutrient dynamics of the nearshore coastal ecosystems especially where direct terrestrial inputs do not contribute significantly to the nutrient budget.  相似文献   

10.
The effect of patchy colonies of the invasive zebra mussel (Dreissena polymorpha) on sedimentary processes was investigated in a mesotrophic lake (Plateliai Lake, Lithuania). Benthic fluxes of O2, TCO2, CH4, Mn2+, Fe2+, N2, the inorganic forms of N, Si and P and dissolved organic C and N were quantified by dark incubations of sediments cores, with and without D. polymorpha. Individual mussels also were incubated for metabolic measurements. Sediments with D. polymorpha had significantly higher O2 and TCO2 fluxes and displayed higher rates of denitrification. The presence of mussels also resulted in higher regeneration of P and N (mostly as ammonium) while the effect on Si was not significant. However, likely due to the low zebra mussel biomass (57.2 ± 25.3 gSFDW m?2), biodeposition has not changed the ratio between anaerobic and total respiration. Methane and reduced metals fluxes were in fact similar in the presence and absence of D. polymorpha. Incubations of mussels without sediments confirmed that bivalve metabolism was the main driver of benthic respiration and nutrient recycling. Nitrate production suggested the presence of nitrifiers associated with the molluscs. The main outcome of this study was that zebra mussels alter the quantity and the stoichiometry of nutrients regenerated by the benthic compartment. The enhancement of nitrogen loss via denitrification, by a factor of 1.5, was much less pronounced than the increase in ammonium recycling rate, stimulated by a factor of 33. Negligible PO4 3? fluxes in bare sediments (?3.4 ± 6.8 μmol m?2 h?1) increased in the presence of mussels and considerable amounts of this nutrient (69.6 ± 29.4 μmol m?2 h?1) were mobilized to the water column. Further research should address other nutrient sources to the lake to verify whether altered rates and stoichiometry of benthic regeneration can affect primary producer community composition and activity.  相似文献   

11.
The coastal zone of the Great Barrier Reef shelf, with an area of 30,000 km(2) and a water volume of 300 km(3), receives an average annual input of sediment on the order of 14-28 Mty(-1)--an estimated two- to fourfold increase since European settlement. There is considerable concern about the impact and ultimate fate of terrestrially-derived nutrients entering the Great Barrier Reef World Heritage Area (GBRWHA). Analysis of current data suggests that microbial communities in coastal waters and in unconsolidated sediments metabolise nutrients equivalent to the entire dissolved and particulate nutrient load debouched from land. River-derived nutrients account for 40-80% of the carbon, 13-30% of the nitrogen, and 2-5% of the phosphorus necessary to support the observed rates of benthic and pelagic mineralisation in Princess Charlotte Bay in the far north, and in Rockingham Bay and Missionary Bay in the central section, of the GBRWHA. Nearly all nitrogen is ultimately returned to the atmosphere via denitrification. There is little net burial of nutrients in subtidal sediments. These budget estimates are based on a sparse data set, but it is clear that marine sources of nutrients (N-fixation by pelagic and benthic cyanobacteria) must be important, but the magnitude of these sources is poorly known and likely to be highly variable in space and time. Data from sediment trap deployments suggest that, despite significant re-suspension, sedimentation fluxes are sufficient to balance benthic mineralisation rates. Most organic material deposited to the benthos appears to be flocculent or colloidal aggregates, perhaps formed via microbial mediation and exudation of extra-cellular material. The geophysical dynamics of the coastal boundary layer plays an important role in concentrating biological and biogeochemical activity within a shallow, narrow coastal zone. Mangroves and tidal flats are small in area, but trap, transform, and store a disproportionate amount of sediment and organic matter within the GBRWHA. The highly efficient use of terrestrially-derived nutrients by benthic and pelagic microbes in the coastal zone helps to explain why coral reefs on the middle and outer shelf have remained relatively unscathed despite a significant increase in sediment delivery.  相似文献   

12.
《Marine pollution bulletin》2013,66(10-12):478-489
Atoll lagoons display a high diversity of trophic states due mainly to their specific geomorphology, and probably to their level and mode of human exploitation. We investigated the functioning of the Ahe atoll lagoon, utilized for pearl oyster farming, through estimations of photosynthetic parameters (pulse amplitude modulation fluorometry) and primary production (13C incorporation) measurements of the size structured phytoplankton biomass (<2 μm and >2 μm). Spatial and temporal scales of variability were surveyed during four seasons, over 16 months, at four sites within the lagoon. While primary production (P) was dominated by the picophytoplankton, its biomass specific primary productivity (PB) was lower than in other atoll lagoons. The variables size fraction of the phytoplankton, water temperature, season, the interaction term station * fraction and site, explained significantly the variance of the data set using redundancy analysis. No significant trends over depth were observed in the range of 0–20 m. A clear spatial pattern was found which was persistent over the seasons: south and north sites were different from the two central stations for most of the measured variables. This pattern could possibly be explained by the existence of water cells showing different water residence time within the lagoon. Photoacclimation strategies of the two size fractions differed through their light saturation coefficient (higher for picophytoplankton), but not through their maximum photosynthetic capacity (ETRmax). Positive linear relationships between photosynthetic parameters indicated that their dynamic was independent of light availability in this ecosystem, but most probably dependent on nutrient availability and/or rapid changes in the community structure. Spatial and temporal patterns of the measured processes are then further discussed in the context of nutrient availability and the possible role of cultured oysters in nutrient recycling.  相似文献   

13.
The Kara Sea is one of the arctic marginal seas strongly influenced by fresh water and river suspension. The highly seasonal discharge by the two major rivers Yenisei and Ob induces seasonal changes in hydrography, sea surface temperature, ice cover, primary production and sedimentation. In order to obtain a seasonal pattern of sedimentation in the Kara Sea, sediment traps were deployed near the river mouth of the Yenisei (Yen) as well as in the central Kara Sea (Kara) within the framework of the German–Russian project “Siberian River run-off; SIRRO”. Two and a half years of time-series flux data were obtained between September 2000 and April 2003 and were analyzed for bulk components, amino acids, stable carbon and nitrogen isotopes as well as sterols and fatty acids.Sediment trap data show that much of the annual deposition occurred under ice cover, possibly enhanced by zooplanktonic activity and sediment resuspension. An early bloom of ice-associated algae in April/May occurred in the polynya area and may have been very important to sustain the life cycles of higher organisms after the light limitation of the winter months due to no/low insolation and ice cover. The strong river input dominated the months June–August in the southern part of the Kara Sea. The central Kara Sea had a much shorter productive period starting in August and was less affected by the river plumes. Despite different time-scales of sampling and trapping biases, total annual fluxes from traps were in the same order of magnitude as accumulation rates in surface sediments. Terrestrial organic carbon accumulation decreased from 10.7 to 0.3 g C m−2 a−1 from the riverine source to the central Kara Sea. Parallel to this, preservation of marine organic matter decreased from 10% to 2% of primary productivity which was probably related to decreasing rates of sedimentation.  相似文献   

14.
The benthic fluxes (diffusive and with chambers) of dissolved inorganic carbon (DIC), dissolved oxygen (DO) and total alkalinity (TA) have been calculated in summertime in the estuary system formed by the mouths of the Tinto and Odiel rivers (SW of Spain). An increase of DIC in interstitial water with depth was found for all stations showing values of up to 28 mM at a depth of 5 cm. The diffusive fluxes of DIC and TA obtained ranging between 1.8–7.8 and 1.5–7.3 mmol m−2 d−1, respectively. These intervals are in agreement with those found for other coastal systems. Considering the plots of DIC vs. alkalinity (ΔDIC/ΔTA) in the first 30 cm of interstitial water, it was deduced that sulphate reduction and the oxidation of sulphides seem to have special relevance in the sediments of the stations studied. The benthic fluxes of inorganic carbon and DO measured by benthic chambers were variable, presenting elevated values (309–433 mmol DIC m−2 d−1 and 50–120 mmol DO m−2 d−1). The most elevated fluxes of DIC were seen at the stations with high anthropogenic influence (close to populated areas and industrial discharges). A great proportion of these fluxes are due to CaCO3 dissolution processes, which constitute an estimated 49% of total DIC flux. DIC and DO benthic flux quotients were far in excess of unity, indicating the significance processes of anaerobic degradation of organic material at the stations studied.  相似文献   

15.
Phaeocystis blooms are of major importance in the Eastern English Channel, where they significantly contribute to spring organic matter input with chlorophyll concentrations commonly higher than 30 microgl(-1) in the water column. Post-bloom deposition of Phaeocystis derived mucilaginous compounds has been shown to have a major importance on benthic intertidal systems, but resulting mineralization processes and consequences on the macrobenthic compartment remain poorly documented in subtidal areas. In this frame, a study was performed along the French coast of the English Channel to quantify mineralization processes, as well as potential consequences on subtidal sediments, especially their geochemistry and associated macrofaunal communities. Seven stations were studied along a depth gradient during four cruises: before (March), during (April, May) and after (June) the spring bloom. Sediment characteristics and organic carbon content were described, as well as sediment-water fluxes of oxygen and ammonium. Macrofaunal characteristics were also analyzed. Stations were chosen as representative of the various benthic communities present in the area, which are directly linked to the granulometric characteristics of the sediments. To account for the general functioning of the water column, characterized by a coastal flow where higher concentrations of Phaeocystis are generally recorded, similar communities were sampled inshore and offshore, when possible: (i) the Abra alba community located only close to the coast, (ii) the Ophelia borealis community located inshore and offshore, and (iii) the Amphioxus lanceolatus community located inshore and offshore. Generally, low exchange rates of oxygen and ammonium were measured (respectively, in the range 50-150 micromol O2 m(-2)h(-1) and -25 to 35 micromol NH4+ m(-2)h(-1)) between the water column and the muddy-sand to coarse sand permeable sediments, as a consequence of the low organic carbon content due to the high hydrodynamic forcing. As a consequence of organic matter accumulation in surficial sediments probably resulting from Phaeocystis post-bloom deposition, an increase of sediment oxygen demand and ammonium release was clearly evidenced up to 660 micromol O2 m(-2)h(-1) and 205 micromol NH4+ m(-2)h(-1) in May, only in stations located close to the coast (<8 kms), in the A. alba community. Despite those significant biogeochemical changes in surficial sediments, no significant consequence was pointed out on macrofauna, neither in the O. borealis and A. lanceolatus communities, nor in the coastal A. alba community. Most of the temporal variations recorded might be attributed to the common spring population dynamics, but this study highlights the potential use of geochemical parameters as a forewarning signal of benthic disequilibrium.  相似文献   

16.
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17.
The effect of resuspension on benthic fluxes of oxygen (O2), ammonium (NH4+), nitrate (NO3?), phosphate (PO43?), silicate (Si(OH)4), dissolved inorganic carbon (DIC), total dissolved iron (Fe) and total dissolved manganese (Mn) was studied at three different stations in the Gulf of Finland (GoF), Baltic Sea during three cruises in June–July 2003, September 2004 and May 2005. The stations were situated on different bottom types in the western, central and eastern part, respectively, of the open GoF. The fluxes were measured in-situ using the autonomous Göteborg benthic lander. To simulate resuspension events, the stirring speed was increased in two of the four chambers of the lander after approximately half of the incubation time. The other two chambers were used as control chambers. Clear effects of resuspension were observed on the oxygen fluxes where an increase of the consumption was observed in 88% of the cases and on average with 59% (stdev=53). The NH4+ fluxes were affected in 50% of the cases (4 out of 8 incubations) at stations with low bottom water oxygen concentrations, but in no cases where the bottom water was oxygenated (0 out of 9 incubations). The NH4+ fluxes decreased by 26±27% in 2005 and by 114±19% in 2003. There was no clear effect of resuspension on the fluxes of any of the other solutes in this study. Thus, resuspension events did not play a significant role in release/uptake of NO3?, PO43?, Si(OH)4, DIC, Fe and Mn in GoF sediments. However, increased oxygen consumption as a result of resuspension may lead to spreading of anoxic/suboxic bottom water conditions, and thus indirectly to increased benthic release of phosphate, ammonium and iron.  相似文献   

18.
: Phytoplankton primary production measurements and sediment trapping in the large (270 km2) shallow (mean depth 2.8 m) Lake Võrtsjärv were performed during ice-free periods in 1995-1996. Sedimentation rate varied from 26 to 700 g DWm-2d-1 (DW=dry weight), with a mean value of 170 g DWm-2d-1. Under the influence of prevailing westerly and south-westerly winds, the sedimentation rate was higher in the northern part, and lower in the western and southern parts of the lake. An increasing trend towards autumn could be followed in both years. The mean sedimentation rates in the dry year 1996 with a low lake water level exceeded those of the “normal” 1995 by a factor of more than two. New sedimentation formed 10-15 % of the downward sediment flux in 1995 and 4-6 % in 1996, while the major part of entrapped matter originated from resuspended bottom sediments. The dynamics of gross sedimentation showed no relation to the primary production but correlated significantly with the concentration of suspended solids, with the average wind speed and with the mean depth of the lake during trap exposition.¶The composition of entrapped matter did not show seasonal variation but differed between the sampling stations. The amount of particulate organic matter (POM) per DW varied from 11 % at places where the bottom sediment consisted of moraine or sand to 28 % at places with muddy bottom. N:POM was rather stable (45-61 mgg-1, Cvar = 6 %). The variability of P:POM (3.5-7.1, Cvar = 20 %) exceeded that of P:DW (0.75-1.31 mgg-1, Cvar = 10 %) showing the essential role of mineral-bound P in the settling material. In these conditions, the N:P ratio was determined by the POM content of settling matter. POM:DW in settling material was generally higher than in the 0-2 cm layer of bottom sediments.  相似文献   

19.
In order to provide an accurate annual rate of net benthic community production, community photosynthetic response to incident irradiance and respiration were measured at different times of the year, at mid-tide level on the muddiest part of the Mont Saint-Michel Bay. As the water turbidity prevented any photosynthesis by the microphytobenthos during immersion periods, primary production was measured only during emersion periods. In contrast respiration was expected to vary according to the tidal cycle and was measured during both emersion and immersion periods. Primary production and respiration rates under emersion were assessed using in situ infra-red gas analysis of CO2 exchange measured in a benthic chamber. Respiration rates under immersion were assessed through total CO2 concentration variations in incubated cores.  相似文献   

20.
Song X  Huang L  Zhang J  Huang X  Zhang J  Yin J  Tan Y  Liu S 《Marine pollution bulletin》2004,49(11-12):1036-1044
Environmental factors, phytoplankton biomass (Chl a) and primary production of two water areas in Daya Bay (Dapeng'ao Bay and Aotou Bay) were investigated during the transition period from spring to summer. Chl a ranged from 3.20 to 13.62 and 13.43 to 26.49 mg m(-3) in Dapeng'ao Bay and Aotou Bay respectively, if data obtained during red tides are excluded. Primary production varied between 239.7 and 1001.4 mg Cm(-2) d(-1) in Dapeng'ao Bay. The regional distribution of Chl a and primary production were mostly consistent from spring to summer in both bays. Seasonal transition characters have been found in Daya Bay from spring to summer, including high values of DO, nitrate and silicate. Size structures of phytoplankton and its primary production do not change very much from spring to summer, with micro-phytoplankton dominating and contributing about 50% of the whole. In Daya Bay, phytoplankton is limited by nitrogen in spring, and by phosphate in summer. Artificial impacts are evident from high temperature effluent from nuclear power stations, aquaculture and sewage. During the investigation, a red tide occurred in Aotou Bay, with a maximum Chl a of 103.23 mgm(-3) at surface and primary production of 2721.9 mg Cm(-2) d(-1) in the red tide center. Raised water temperature and nutrient supply from land-sources help to stimulate annual red tides.  相似文献   

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