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1.
Abstract

Bacterial numbers and production were measured in the upper water column in the winter and spring of 1993 in five water masses surrounding the South Island of New Zealand. Average bacterial numbers and production were found to be higher in spring (8.5 × 105 cells ml?1 and 0.20 mg m3 h?1, respectively) than winter (5.5 × 105 cells ml?1 and 0.05 mg C m3 h?1 respectively). Bacterial production was strongly correlated with chlorophyll a and primary production (P < 0.001) in spring but not in winter. Spring bacterial production and at 10 m depth averaged across 28 stations was 23% of primary production, and with a growth efficency of 40%, may have consumed up to 57% of primary production. Bacterial biomass was greater than phytoplankton biomass for 75% of the 10 m depth comparisons during winter sampling and 44% during the spring sampling. The bacterial biomass was found to represent 24.6–33.5% of the nitrogen in particulate organic matter (<200 μm) supporting the concept that in New Zealand oceanic water masses bacteria are of significant biogeochemical importance.  相似文献   

2.
Abundance distribution and cellular characteristics of picophytoplankton were studied in two distinct regions of the equatorial Pacific: the western warm pool (0°, 167°E), where oligotrophic conditions prevail, and the equatorial upwelling at 150°W characterized by high-nutrient low-chlorophyll (HNLC) conditions. The study was done in September–October 1994 during abnormally warm conditions. Populations of Prochlorococcus, orange fluorescing Synechococcus and picoeukaryotes were enumerated by flow cytometry. Pigment concentrations were studied by spectrofluorometry. In the warm pool, Prochlorococcus were clearly the dominant organisms in terms of cell abundance, estimated carbon biomass and measured pigment concentration. Integrated concentrations of Prochlorococcus, Synechococcus and picoeukaryotes were 1.5×1013, 1.3×1011 and 1.5×1011 cells m−2, respectively. Integrated estimated carbon biomass of picophytoplankton was 1 g m−2, and the respective contributions of each group to the biomass were 69, 3 and 28%. In the HNLC waters, Prochlorococcus cells were slightly less numerous than in the warm pool, whereas the other groups were several times more abundant (from 3 to 5 times). Abundance of Prochlorococcus, Synechococcus and picoeukaryotes were 1.2×1013, 6.2×1011 and 5.1×1011 cells m−2, respectively. The integrated biomass was 1.9 g C m−2. Prochlorococcus was again the dominant group in terms of abundance and biomass (chlorophyll, carbon); the respective contributions of each group to the carbon biomass were 58, 7 and 35%. In the warm pool the total chlorophyll biomass was 28 mg m−2, 57% of which was divinyl chlorophyll a. In the HNLC waters, the total chlorophyll biomass was 38 mg m−2, 44% of which was divinyl chlorophyll a. Estimates of Prochlorococcus, Synechococcus and picoeukaryotes cell size were made in both hydrological conditions.  相似文献   

3.
Vertical distributions of phytoplankton biomass, compositions and size structure were investigated during the spring-intermonsoon (April 22 to 30) of 2010 along transact 10°N of the Bay of Bengal, northern Indian Ocean. Surface phytoplankton biomass (Chl a) was (0.065§0.009) μg/L, being greater than 80% of which was contributed by pico-phytoplankton (<3 μm). The Chl a concen- tration vertically increased to the maximal values at deep chlorophyll maximum (DCM) layer that shoaled eastwards from 75 to 40 m. The Chl a biomass at DCM layer generally varied between 0.2 and 0.4 μg/L, reaching the maximum of 0.56 μg/L with micro-phytoplankton cells (>20 μm) accounting for 58% and nano- (3-20 μm) or pico-cells for 15% and 27%, respectively. In particular, the cells concentration coupling well with phosphate level was observed at middle layer (75-100 m) of 87° to 89°E, dominated by micro-cells diatoms (e.g., Chaetoceros atlanticus v. neapolitana, Chaetoceros femur and Pseudonitzschia sp.) and cyanobacteria (i.e., Trichodesmium hildebrandtii), with the cells concentration reached as high as 4.0×104 and 4.3×104 cells/L. At the rest of the trans- act however, dino°agellates (e.g., Amphisdinium carterae and Prorocentrum sp.) were the dominant species, with the cells concentration varying from 0.3×103 to 6.8×103 cells/L. Our results also in- dicate that the regulation of large cells (micro-, nano-) on phytoplankton biomass merely occurred at DCM layer of the Bay.  相似文献   

4.
We measured the in situ primary production at four stations from the surface to 80 m off Sanriku in late May 1997. The depth-integrated daily primary production in the upper 80 m was estimated to be 391, 468, and 855 mgC m−2d−1 in water from the Oyashio, and 336 mgC m−2d−1 in the warm-core ring. The variation in the primary production was primarily due to the variation in phytoplankton activity (chlorophyll α-specific primary production). A combination of previous and present studies in water from the Oyashio and the warm-core ring suggested that phytoplankton activity is proportional to light intensity between 12 and 50 Ein m−2d−1 which is close to the usual light condition (61–75 Ein m−2d−1) off Sanriku in May and June. Light may be a limiting factor for phytoplankton off Sanriku in late spring and early summer.  相似文献   

5.
通过计算机图像测定系统测定、计算获得海冰细菌的大小、面积和碳含量,研究了北极巴伦支海和拉普捷夫海的浮冰中细菌大小、丰度和生物量的垂直分布及其与海冰微藻生物量的关系.细菌在冰心中是非均匀分布的,至少有两种不同分布类型:第一类有单一的丰度峰值,在冰心底部或在冰心中部;第二类有两个丰度峰值.海冰中细菌的丰度为0.4×105～36.7×105个/cm3.不同类型海冰中的细菌大小变化极大,在多年冰中,最大的细菌与叶绿素a最大值出现在同一层,而在一年冰中,细菌大小几乎没有垂直变化.整柱冰心的细菌生物量变化为19.2～79.2mg/cm2,细菌与海冰微藻生物量之比为0.43～10.00.对固定冰比较和研究的结果发现,海冰冰心中细菌大小、丰度和生物量的垂直分布差别极大.据此,分析了对目前海冰研究采样方法的局限性,并提出了规范采样方法的设想.  相似文献   

6.
Phytoplankton and its relationships with physical and chemical variables were analysed over a 2-year period in Hueihue and Linao Bays (southern Chile). Samples were collected on a monthly basis from May 1991 to May 1993. The growth rate of a single stock of hatchery-produced oysters (Ostrea chilensis) distributed between these two bays was also monitored monthly. The growth rate of oysters maintained at Linao Bay (site associated with a fish farm) was significantly higher, at every depth, compared with the oysters maintained at Hueihue Bay. Temperature and salinity values and their annual fluctuations were similar at both locations, presenting higher variations at the surface (1 m) due to the influence of air temperature and local precipitation than at depth. However, significant differences in phytoplankton abundance and composition were found between the two locations. The phytoplankton community was characterized by high biomass values during spring and summer, the dominance of diatoms and an inverse relationship between temperature and species diversity. However, phytoplankton cell abundance, biovolume and chlorophyll a concentration were significantly higher at Linao at every depth sampled. Cell abundance ranged between 4.49 × 104 and 7.45 × 106 cells · l?1 in Hueihue and between 6.48 × 104 and 8.71 × 106 cells ·1?1 in Linao. The influence of temperature on chlorophyll a concentration was significant except at 8 m at both locations. The instantaneous oyster growth rate was found to be positively correlated with temperature, chlorophyll a concentration and particulate organic matter at both locations. A significant negative relationship between oyster growth and amount of particulate inorganic matter was found; this confirms the important role played by seston composition in oyster growth. The demonstration of variation in oyster growth rate associated with differences in food availability between the two locations provides insight into the ecological role played by fish farms in southern Chile. The results suggest a strong link between food availability and oyster growth.  相似文献   

7.
Seasonal variations in the picoplankton community were investigated from June 2002 to March 2004 within the photic zone of Sagami Bay, Japan. The study area was mostly dominated by coastal waters during the warm period (mixed layer water temperature ≥ 18°C). During the cold period (mixed layer water temperature ≤ 18°C), the water mass was characterized by low temperature and high saline waters indicative of the North Pacific Subtropical Mode Water (NPSTMW). Occasionally, a third type of water mass characterized by high temperature and low saline properties was observed, which could be evidence of the intrusion of warm Kuroshio waters. Synechococcus was the dominant picophytoplankton (5−28 × 1011 cells m−2) followed by Prochlorococcus (1−5 × 1011 cells m−2) and picoeukaryotes during the warm period. Heterotrophic bacteria dominated the picoplankton community throughout the year, especially in the warm period. During the Kuroshio Current advection, cyanobacterial abundance was high whereas that of picoeukaryotes and heterotrophic bacteria was low. During the cold period, homogeneously distributed, lower picophytoplankton cell densities were observed. The dominance of Synechococcus in the warm period reflects the importance of high temperature, low salinity and high Photosynthetically Active Radiation (PAR) on its distribution. Cyanobacterial and heterotrophic bacterial abundance showed a positive correlation with temperature. Prochlorococcus and picoeukaryotes showed a positive correlation with nutrients. Picoeukaryotes were the major contributors to the picophytoplankton carbon biomass. The annual picophytoplankton contribution to the photosynthetic biomass was 32 ± 4%. These observations suggest that the environmental conditions, combined with the seasonal variability in the source of the water mass, determines the community structure of picoplankton, which contributes substantially to the phytoplankton biomass and can play a very important role in the food web dynamics of Sagami Bay.  相似文献   

8.
胶州湾夏季异养浮游细菌的时空变化规律及影响因素   总被引：3，自引：0，他引：3  
2001年夏季对胶州湾异养浮游细菌在一个潮周期内的变化规律及影响因素进行了研究。结果表明,胶州湾异养浮游细菌数量的垂直分布特征是表层大于底层,表层平均8.99×109个/L,底层平均5.23×109个/L。胶州湾水体异养浮游细菌日变化幅度在表层水体较为明显,底层相对较小,但其变化规律均为最高值在小潮期而最低值出现在大潮期。浮游动物摄食、浮游植物光合作用产生的溶解有机物及水温和日光中的紫外辐射是影响胶州湾异养浮游细菌昼夜变化的主要因素,水交换是影响其日变化的主要因素。  相似文献   

9.
河北沿岸微微型浮游植物的分布特征   总被引：1，自引：0，他引：1  
于2006年7月～ 2007年10月间,分4个季度调查了河北省沿岸微微型浮游植物的丰度和生物量及对浮游植物总生物量的贡献.结果显示:河北近岸海域聚球藻蓝细菌丰度为4.46×103个/mL(0.79×103～ 16.19×103个/mL),生物量(以碳计,下同)为1.31 mg/m3 (0.84～17.47 mg/m3),季节分布特征为秋季＞冬季＞夏季＞春季.微微型光合真核生物丰度为4.43×102个/mL (0.84×102～ 17.47×102个/mL),生物量为1.11mg /m3 (0.21～ 4.37 mg/m3),季节变化变现为秋季＞冬季＞春季＞夏季.微微型浮游植物对浮游植物总生物量的贡献年平均为5.32％(1.84％～ 8.91％),春季最高,秋季最低.温度在较冷季节(冬春季)里是影响聚球藻蓝细菌生长和分布的控制因素.总之,在近岸环境里,微微型浮游植物并不占优势.  相似文献   

10.
New maps of the mean monthly distribution of chlorophyll and the primary production in the Kara Sea were compiled using joint processing of CZCS (1978–1986), SeaWiFS (1998–2005), and MODIS (2002–2006) satellite data and field measurements. The annual primary production of phytoplankton is estimated at 22.3 × 106 t of C per year or 70 mg of C/m2 per day. The results of the calculations of the organic carbon budget in the Kara Sea are presented.  相似文献   

11.
Abstract

The influence of density stratification on sedimentation, suspension, and resuspension in Tasman Bay and Beatrix Bay, New Zealand, two contrasting coastal environments, was studied with specific reference to the implications for modelling aquaculture sustainability. Tasman Bay, an enhanced scallop (Pecten novaezelandiae Reeve) fishery, is a very large coastal indentation gently shelving to c. 20 m deep c. 10 km from shore and open to the Tasman Sea, whereas Beatrix Bay, an area of intense Greenshell? mussel (Perna canaliculus Gmelin) aquaculture, is a small (22 km2 × 30–40 m deep) enclosed embayment off the side of the nearby Pelorus Sound. Sediment trap arrays were used to determine the vertical fluxes of suspended solids and the associated chlorophyll component. Benthic chambers were used to investigate sediment nutrient regeneration. In summer, salinity gradients in both bays are minimal or non‐existent because of low inputs of fresh water and density stratification is mainly controlled by water temperature. The data from mid summer exhibited different spatial distribution patterns for detritus and phytoplankton biomass (as indicated by chlorophyll) in these two very different bays, although they had similar turbulent environments. The density discontinuity at the thermocline had a strong influence on settling of phytoplankton. There was evidence of upwards entrainment of suspended paniculate matter into the upper water column from the thermocline in Beatrix Bay. Benthic resuspension was estimated to contribute up to 90% of the suspended solids caught in sediment traps near the sea floor in both bays. The trapping rate of phytoplankton was thought to be dependent on species dominance. Possible mechanisms of resuspension included turbulence in the benthic boundary layer, and high velocities below the thermocline associated with internal seiches. The presence of a mid water column chlorophyll maximum in Beatrix Bay is discussed in terms of nutrient and light regimes at the thermocline, and species composition. In Tasman Bay, the chlorophyll maximum was thought to be caused by resuspension of benthic microphytes and their subsequent confinement in a thin layer (2–4 m thick) of high turbulence between the thermocline and the seabed.  相似文献   

12.
The KwaZulu-Natal Bight is a shallow indentation of the eastern seaboard of South Africa, characterised by a narrow (45 km wide) extension of the continental shelf, with a shelf break at about 100 m. It has a complex hydrography: the waters of the bight are derived from the fast-flowing, southward-trending Agulhas Current, which is fed mostly by the tropical and subtropical surface waters of the South-West Indian Ocean subgyre, which are generally oligotrophic in nature, notably depleted in reduced nitrogen and phosphate except at river mouths and during periodic upwelling of deeper nutrient-rich water. Despite this, the bight is believed to be relatively productive, and it is suggested that efficient nutrient recycling by prokaryotes may sustain primary productivity efficiently, even in the absence of new nutrient inputs. Here we have measured bacterial numbers, biomass and heterotrophic productivity during summer and winter in conjunction with phytoplankton standing stock and factors that influence it. Bacterial distribution closely matched phytoplankton distribution in surface waters, and was highest close to the coast. Bacterial standing stocks were similar to those of oligotrophic systems elsewhere (0.5–5.0 × 105 cells ml–1; 1 × 10–8 to 1.25 × 10–7 g C ml–1) and increased in association with the development of phytoplankton blooms offshore and with inputs of allochthonous material by rivers at the coast. Heterotrophic productivity in summer was lowest in the far south and north of the bight (0.5 × 10–10 g C ml–1 h–1) but higher close to the shore, over shallow banks, and in association with increased phytoplankton abundance over the midshelf (1.0–3.5 × 10–9 g C ml–1 h–1). There were marked seasonal differences with lower bacterial standing stocks (5 × 104 to 2 × 105 cells ml–1; 4–5 × 10–9 to 1–2 × 10–8 g C ml–1) and very low bacterial productivity (4 × 10–11 to 1 × 10–10 g C ml–1 h–1) in winter, probably resulting from lowered rates of primary productivity and dissolved organic matter release as well as reduced riverine allochthonous inputs during the winter drought.  相似文献   

13.
杨春蕙  刘琦  王迎宾 《海洋与湖沼》2022,53(5):1219-1224
当渔业资源出现衰退时,加强资源增殖放流以养护渔业资源、提高渔业产量对于渔业资源可持续利用具有重要意义;与此同时,增殖放流的实施会对基于资源开发与管理的评估的结果产生影响。基于2001~2015年间东海北部海域三疣梭子蟹(Portunus trituberculatus)渔业数据,采用增殖剩余产量模型,对东海北部海域三疣梭子蟹的最大可持续产量(MSY)及取得MSY时所需捕捞努力量(EMSY)和原存生物量(BMSY)进行了评估,并与传统Schaefer模型评估结果进行了比较。结果表明,当年增殖放流量约在3×106~95×106尾之间时,三疣梭子蟹年产量逐渐增加, MSY在14.2×104 t和14.6×104 t之间, EMSY基本在15×104吨位左右。增殖放流量增加,其对应的MSY也越高,能承受的EMSY也越高(从15×104~15.4×104吨位之间),相反BMSY则减小(从188.4×104 t降至186.6×104 t)。与传统的Schaefer模型评估结果相比,增殖剩余产量模型由于考虑了增殖放流生物量的因素,得到了MSY和EMSY有所增加,而BMSY有所下降的结论。研究结果有望为该研究海域三疣梭子蟹可持续地捕捞、放流与管理提供科学依据。  相似文献   

14.
The community composition,abundance and culturablity of heterotrophic bacterioplankton in the Dapeng Bay of the South China Sea were investigated by morphological method,bacterial cultivation and biochemical methods over an annual cycle.Aeromonas and Pseudomonas were the predominant genera among the Gram-negative bacteria.The bacterioplankton abundance fluctuated from 2.07×10 8 to 2.44×10 9 cells/dm 3 ,and culturable bacteria abundance ranged between 0.1×10 6 and 16.07×10 6 CFU/dm 3 .The Culturablity of heterotrophic bacteria ranged between 0.01% and 1.31%.The relationship between bacterial culturablity and the environmental factors was also studied in different sites of the Dapeng Bay.Throughout the bay,a significantly positive relationship was evidenced between bacterial culturability and temperature,meanswhile bacterial culturability was significantly inversely related with salinity.The positive relationship was shown at the central bay while a negative relationship was observed at the bay mouth and there was no significant correlation at top bay between bacterial culturablity and chlorophyll a of sea water.A positive relationship was found between culturability and DIN all the bay,but DIP showed a significantly negative relationship with bacterial culturability only at the mouth of the bay.  相似文献   

15.
春季黄海浮游植物生态分区:物种组成   总被引：3，自引：1，他引：2  
Phytoplanktonic ecological provinces of the Yellow Sea(31.20°–39.23°N, 121.00°–125.16°E) is derived in terms of species composition and hydrological factors(temperature and salinity). 173 samples were collected from 40 stations from April 28 to May 18, 2014, and a total of 185 phytoplanktonic algal species belonging to 81 genera of 7phyla were identified by Uterm?hl method. Phytoplankton abundance in surface waters is concentrated in the west coast of Korean Peninsula and Korea Bay, and communities in those areas are mainly composed of diatoms and cyanobacteria with dominant species of Cylindrotheca closterium, Synechocystis pevalekii, Chroomonas acuta,Paralia sulcata, Thalassiosira pacifica and Karenia mikimotoi, etc. The first ten dominant species of the investigation area are analyzed by multidimensional scaling(MDS) and cluster analysis, then the Yellow Sea is divided into five provinces from Province I(P-I) to Province V(P-V). P-I includes the coastal areas near southern Liaodong Peninsula, with phytoplankton abundance of 35 420×10~3–36 163×10~3 cells/L and an average of 35 791×10~3 cells/L, and 99.84% of biomass is contributed by cyanobacteria. P-II is from Shandong Peninsula to Subei coastal area. Phytoplankton abundance is in a range of 2×10~3–48×10~3 cells/L with an average of 24×10~3cells/L, and 63.69% of biomass is contributed by diatoms. P-III represents the Changjiang(Yangtze River) Diluted Water. Phytoplankton abundance is 10×10~3–37×10~3 cells/L with an average of 24×10~3 cells/L, and 73.14% of biomass is contributed by diatoms. P-IV represents the area affected by the Yellow Sea Warm Current.Phytoplankton abundance ranges from 6×10~3 to 82×10~3 cells/L with an average of 28×10~3 cells/L, and 64.17% of biomass is contributed by diatoms. P-V represents the cold water mass of northern Yellow Sea. Phytoplankton abundance is in a range of 41×10~3–8 912×10~3 cells/L with an average of 1 763×10~3 cells/L, and 89.96% of biomass is contributed by diatoms. Overall, structures of phytoplankton community in spring are quite heterogeneous in different provinces. Canonical correspondence analysis(CCA) result illustrates the relationship between dominant species and environmental factors, and demonstrates that the main environmental factors that affect phytoplankton distribution are nitrate, temperature and salinity.  相似文献   

16.
Seismic data and cores from the Waitaki continental shelf, New Zealand, indicate a major reduction in terrigenous deposition about 10,000 years ago when the accumulation of extensive marine sand wedges ceased. This change reflects the impact of lacustrine traps on the main sediment supplier to the shelf, the Waitaki River. Prior to 10,000 years BP, lakes Ohau, Pukaki and Tekapo were glaciated and glacio-fluvial detritus was fed directly to the river and shelf where marine deposition was ca. 6.8×106 t/yr. Following deglaciation, the newly created lakes acted as efficient sediment traps that denied the river 22.2×106 t/yr. Accordingly, modern shelf deposition is around 0.04×106 t/year.  相似文献   

17.
2009年8,10,12月及2010年3月分别对烟台四十里湾的12个站位开展了四个航次的季节调查.研究发现浮游植物3门45属73种,其中硅藻46种,甲藻24种,褐胞藻3种.硅藻是构成调查区域浮游植物群落的主要类群.浮游植物种类与数量呈现出明显的季节变化特征.夏季(8月)物种数最多(57种),秋季(10月)次之(40种)...  相似文献   

18.
微微型浮游植物是水环境生态碳汇的重要基石之一,也是初级生产的重要执行者。选取了一个典型的陆海交界关键带环境——海南东寨港入海口水域,采集了东寨港红树林保护区开阔水域、入港河流和新埠海海端的微微型浮游植物的样品,通过流式细胞仪分析技术对样品进行分析,以探究它们在东寨港水域中的丰度、分布及环境指示意义。结果表明,冬季水域微微型浮游植物以真核浮游植物(Eukaryote,Euk)和聚球藻(Synechococcus,Syn)两大类群为主,其中聚球藻有两个亚群,分别为富含藻蓝蛋白聚球藻(Phycocyanin-rich,PC)和富含藻红蛋白聚球藻(Phycoerythrin-rich,PE)。Syn-PC、Syn-PE和Euk在东寨港水域表层水体的平均丰度分别为(2.61×104±1.09×104)、(3.06×104±7.05×103)、(1.56×105±8.03×104) cells/m L,底层水体的平均丰度分别为(2.64×104±...  相似文献   

19.
Available data on phytoplankton and bacterial abundance and production off the coasts of southern Africa (to the 500 m depth contour) have been assembled and analysed for a network analysis of carbon flow in the Benguela ecosystem. Phytoplankton carbon biomass (from measurements of chlorophyll a) in the northern Benguela (2 558 300 tons) was considerably higher than in the southern Benguela (671 420 and 516 400 tons for the West and South coasts respectively). However, overall annual production (from C14-uptake measurements) was similar, 77 416 608, 76 399 973 and 78 988 020 tons C·year?1 respectively. Phytoplankton respiration and sedimentation losses were calculated as functions of primary production and therefore followed similar trends. From the most conservative estimates (mean bacterial biomass of 10 mg C·m?3 and average P:B of 0,2·day?1) bacterial biomass is 2–7 per cent of phytoplankton biomass in the northern and southern Benguela, and bacterial production is 3–5 per cent of primary production. Assuming a net growth yield of 30 per cent, bacteria would need to consume 9–15 per cent of the total primary production in order to meet their requirements for carbon consumption. Calculations based on a mean bacterial biomass of 40 mg C·m?3 and a mean growth rate of 0,5·day?1 in the upper 30 m of the water column show bacterial biomass to be 8–27 per cent of phytoplankton biomass and bacterial production to be 26–44 per cent of phytoplankton production. Bacterial carbon consumption requirements at these rates amount to 86–147 per cent of total primary production.  相似文献   

20.
The results are presented from three hydrogrpahic surveys in April 1979 of a 40 × 50 km region of the Celtic Sea, centred at 7°W and 51°N, using a towed undulating sensor system. In the 512 days between Surveys 1 and 2, the seasonal thermocline was established, with surface to bottom temperature differences reaching 1.5°C, the average surface chlorophyll a level increased from ～ 1 to ～ 5.5 mg m?3 due mainly to the growth of diatoms, and the surface nitrate concentration decreased from 6 to 1 μM. The third survey was carried out after a further two days and, although surface properties changed little, there was a general deepening of the mixed layer due to stronger winds, and a further increase in the standing stock of phytoplankton.By applying appropriate techniques of horizontal spatial averaging, which took into account possible advective effects, a quantitative comparison was made of the changes at two positions in the survey area which showed significant differences in the rate of development of the phytoplankton population. A simple model of phytoplankton growth was then developed, based on calculations of eddy diffusivity, on measurements of rates of photosynthetic carbon assimilation, and on observations of carbon to chlorophyll ratios, subsurface light attenuation and inorganic nutrient levels. In the absence of any data on zooplankton populations, the loss of phytoplankton by grazing was left as a free parameter.The model was only partly successful in reproducing the observed changes in chlorophyll concentrations during the first 512 days and showed serious limitations for the subsequent 2 days. However, it emphasised several features of the dynamics of spring phytoplankton populations which require further experimental or observational investigation. These include more precise measurements of carbon to chlorophyll ratios and grazing pressure to which the model is sensitive over a rather narrow range (this has important implications in terms both of control by grazing and nutrient limitation), the potential significance of physiological photoadaptation by the plant cells in determining their vertical distribution, and the role of eddy diffusion across the developing thermocline in relation to the sinking of phytoplankton cells and the upward mixing of inorganic nutrients.  相似文献   

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