Phytoplankton community primary productivity

Fig. 1. Model depicting nitrogen flows in a kelp bed community. Primary production by macrophytes is partitioned into particulate (POM) and dissolved (DOM) components. Filter-feeders feed on detritus consisting of POM, bacteria and animal faeces. Recycling of nitrogen via the feedback loop provided by faeces is indicated by heavy lines. Fig. la) shows the model under downwelling conditions, when phytoplankton is imported with surface water from offshore. Fig. lb) shows the model under upwelling conditions when it is assumed that phytoplankton in the upwelling water is negligible and excess detritus is exported in surface water.

Differences in integration time scales may also affect our perception of key derived parameters such as the ThE ratio (Cochran et al. 2000). This ratio (see above) compares the POC flux derived from water column " Th profiles (and thus integrating into the past) with present primary production. As classically measured using incubation techniques, primary production is an instantaneous measurement representing the phytoplankton community as sampled at a single time. Under bloom conditions, the export of POC may lag the production of fresh organic matter and ThE ratios calculated late in a bloom may be overestimates. 

Phaeocystis sp. (Prymnesiophyceae). II. Pigment Composition. J Phycol 34 496-503 Wells ML (1999), Manipulating iron availability in nearshore waters. Limnol Oceanogr 44 1002-1008 Wells ML, Price NM, Bruland KW (1994) Iron limitation and the cyanobacterium Synechococcus in equatorial Pacific waters. Limnol Oceanogr 39 1481-1486 Worthen DL, Arrigo KR (2003) A coupled ocean-ecosystem model of the Ross Sea. Part 1 Interannual variability of primary production and phytoplankton community structure. In DiTullio GR, Dunbar RB (eds) Biogeochemistry of the Ross Sea. Antarct Res Ser 78 93-105... 

Smith EM (1998) Coherence of microbial respiration rate and cell-specific bacterial activity in a coastal planktonic community. Aquat Microb Ecol 16 27-35 Smith WO Jr, Nelson DM, DiTullio GR, Leventer AR (1996) Temporal and spatial patterns in the Ross Sea phytoplankton biomass, elemental composition, productivity and growth rates. J Geophys Res 101 18455-18466 Smith WO Jr, Marra J, Hiscock MR, Barber RT (2000) The seasonal cycle of phytoplankton biomass and primary productivity in the Ross sea, Antarctica. Deep-Sea Res II 47 3119-3140... 

Figure 11.6 Results from seasonal in situ bioassays in the southwest basin of Pamlico Sound. Bars are means of 5 replicates and error bars are on standard deviation.The top panel shows the response of primary productivity of the natural phytoplankton community to the addition of nitrate (+N, 20 pM-N), phosphate (+P, 5 pM-P), nitrate and phosphate (+NP), and the un-amended control.The bottom panel shows the response of chlorophyll a to the same treatments. Relative to controls, strong N limitation was observed in Pamlico Sound despite high load of N to the upstream Neuse River Estuary.

J. McGowan, T. Hayward, E. Venrick and others, CLIMAX time-series Pioneering research on rates and regulation of primary production, including nutrient limitation studies of environmental heterogeneity and phytoplankton community structure dynamics of deep chlorophyll maximum layer studies of N2 fixation DON distributions and dynamics studies of primary N02 maximum layer analytical methods development and improvement centered at, or near, the CLIMAX site (28°N, 155°W)... 

Witek, Z., Ochocki, S., Maciejowska, M., Pastuszak, M., Nakonieczny, J., Podgorska, B., Kownacka, J. M., Mackiewicz, T., Wrzesihska-Kwiecieh, M., 1997. Phytoplankton primary production and its utilization by the pelagic community in the coastal zone of the Gulf of Gdansk (Southern Baltic). Marine Ecology Progress Series, 148, 169-186. 

Although nitrogen is the element primarily controlling eutrophication in estuaries and coastal seas, and phosphorus is the element primarily controlling eutrophication in lakes, other elements can have a major influence on the community structure of aquatic ecosystems and can influence the nature of the response to eutrophication. A key element in this regard is silica (silicon), an element required by diatoms. The availability of silica in a water body has little or no influence on the overall rate of primary production, but when silica is abundant, diatoms are one of the major components of the phytoplankton. When silica is in low supply other classes of algae dominate the phytoplankton composition. 

Today it is generally believed that natural UVR is a strong environmental factor affecting both productivity and community structure in marine and fresh water ecosystems. In open marine waters, both UV-B (280 to 315 nm) and UV-A (315 to 400 nm) reduce phytoplankton primary production (see also Chapter 11) and bacterial production [1,2]. UVR has been demonstrated to influence the structure of marine and fresh water phytoplankton communities [3,4]. 

The salinity of water bodies (Box 3.1) has an effect on the composition of primary producer communities. Fresh water and seawater in typical open marine environments contain the greatest numbers (diversity) of species. However, relatively few organisms can tolerate large fluctuations in salinity (e.g. where fresh water meets seawater in estuaries) and hypersaline conditions. In hypersaline conditions (Box 3.1) phytoplanktonic diversity is much reduced but the species adapted to these environments can produce large amounts of organic material. In addition, herbivore abundance may be low, so much of the net primary production may be available for incorporation into sediments. Cyano-bacterial mat communities tend to be successful in the shallow areas of such environments, and productivity can reach 8-12gCor m-2 day-1 (Schidlowski 1988). °rB... 

There are latitudinal variations in the major families of phytoplankton responsible for marine primary production. Diatoms appear particularly important at high latitudes and along the equatorial belt, but in intermediate latitudes dinoflagellates and coccohthophores are more important. Cyanobacteria and the related prochlorophytes appear to make a major contribution within 40° of the equator. There can also be variations in phytoplanktonic communities with depth. For example, in the subtropical mid-Pacific diatoms are responsible for c.80-90% of total algal production in the... 

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