Temporal Variability Of Phytoplankton Research Articles

Spatial and temporal variation in barnacle growth in a coastal upwelling system

Recent studies suggest that large-scale variation in nearshore primary productivity may strongly influence the dynamics of rocky intertidal communities. Among the hypothesized effects is a link between phytoplankton abundance and the growth of barnacles and other suspension feeders. We tested the strength of this association on the central coast of Oregon, USA, by quantifying water- column chlorophyll a (chl a) concentration and the growth of 2 intertidal barnacles (Balanus glandula and Chthamalus dalli). Barnacles were photographed at 13 d intervals on mid-intertidal growth plates attached in wave-exposed and wave-protected habitats at 2 sites differing in nearshore pro- ductivity: Strawberry Hill (SH) and Boiler Bay (BB), Oregon. B. glandula grew more rapidly in wave- exposed areas than wave-protected habitats, presumably because higher flows delivered more food to passively feeding barnacles. After several months, individuals of both species attained a larger size at SH, the site with consistently higher chl a concentrations. Surprisingly, short-term growth rates only partially matched spatial and temporal variations in phytoplankton. Growth rates were low dur- ing a persistent upwelling event, and increased 2- to 3-fold during the subsequent upwelling relax- ation. At SH, this increase coincided with a major phytoplankton bloom, but growth rates remained high well after chl a concentrations decreased. Moreover, parallel increases in growth were observed at BB, despite the fact that no bloom was recorded at this site. These results imply that factors other than phytoplankton contributed to variation in barnacle growth. Records of barnacle settlement sug- gest that water-column concentrations of larvae increased dramatically at both sites during the period of high barnacle growth. Published analyses of stomach contents indicate that zooplankton may be an important food source in other barnacle species. Yet another factor, water temperature, was also elevated during the period of sustained barnacle growth. Increased barnacle growth during the upwelling relaxation may thus have arisen from the combined benefits of more phytoplankton, more zooplankton, and warmer water temperatures. Incorporating the influence of zooplankton and water temperature into studies of bottom-up influences may improve our ability to explain variation among intertidal communities.

Relationships between Phytoplankton Standing Crop and Physical, Chemical, and Biological Gradients in the Suwannee River and Plume Region, U. S. A.

The Suwannee River (USA) is an amber stained, nutrient rich, blackwater river which flows into relatively clear oceanic waters resulting in the formation of a coastal region with unique physical, chemical, and biological gradients. The intent of this study was to describe the spatial and temporal variability of phytoplankton as it relates to these gradients. Ten stations along a transect ranging from 5 km up river to 31 km offshore, were sampled during four different flow regimes. All four sampling periods included in our study of the Suwannee River and plume region exhibited a similar pattern of phytoplankton abundance; low phytoplankton biomass in the Suwannee River and offshore stations with an area of elevated biomass seaward of the Suwannee River outflow. The results of our analysis of light and nutrient limitation in the region support the hypothesis that this spatial pattern of phytoplankton abundance is strongly influenced by color dependent light limitation in the river and outflow area, combined with nutrient limitation offshore. Our results suggest that both light and nutrient availability control abundance and composition of phyto plankton in this coastal area.

Influences of physical processes on the ecosystem in Jiaozhou Bay: A coupled physical and biological model experiment

In this paper we have used a three‐dimensional coupled physical and biological model to examine the marine ecosystem of Jiaozhou Bay. Physical processes included (1) the M2 tide, (2) river discharges, and (3) winds. The biological model described a simple, phosphorous‐based, lower trophic food web system. The model results showed that tidal mixing had a direct impact on temporal and spatial distributions of nutrients and phytoplankton as well as on shellfish aquaculture. Nutrients and phytoplankton were well mixed vertically by tidal motion. Their concentrations were highest around northwestern and northern regions of the bay near river sources and decreased with water depth from the inner bay to the outer bay. A phytoplankton bloom can occur around the northwestern coast due to the “accumulation” of nutrients under southeasterly wind conditions. The flux analysis suggests that in summer the nutrients in Jiaozhou Bay was directly supplied and maintained by physical processes, but the temporal variation of phytoplankton was controlled dominantly by biological processes associated with nutrient uptake, grazing by zooplankton, and consumption by shellfish. Shellfish aquaculture can modify the bay‐scale balance of the ecosystem in Jiaozhou Bay. The loss of phytoplankton in shellfish aquaculture sites tended to be compensated by advection and diffusion from the surrounding waters. A large consumption of phytoplankton by shellfish can cause a net flux of phytoplankton from the Yellow Sea to Jiaozhou Bay, although there was a net nutrient flux flowing out of the bay. The physical mechanism for the water exchange between Jiaozhou Bay and the Yellow Sea was controlled mainly by a chaotic process associated with nonlinear interactions between oscillating tidal currents and double residual eddies.

A Reply to Sell, Carney, and Fahnenstiel

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Temporal variability of phytoplankton in tropical lakes.

Temporal variability of ecological systems continues to receive theoretical and empirical attention but remains inadequately documented at low latitudes. Results of my comparative investigation of photosynthetic rates of phytoplankton in 6 equatiorial African lakes and similar information from 20 South American, Asian and African lakes studied by others provide the data for an assessment of the range of seasonal variability (expressed as coefficients of variation, CV) among tropical lakes. Sampling intervals varied from 1 week to 3 months and usually spanned at least one year. Within Africa the coefficient of variation ranged from 15% to 61%, and among all the lakes the coefficient of variation ranged from 15% to 86%. The Spearman rank correlation coefficient of the CV's of photosynthesis versus latitude is 0.24 and is not significant at the 0.05 level.Coefficients of variation of photosynthetic rates of phytoplankton in a diverse set of 45 temperate and arctic lakes ranged from 29% to 155% and were significantly different from the set of 26 tropical lakes by the Mann-Whitney U test. When all 71 lakes are compared, the Spearman rank correlation coefficient of CV's of photosynthesis versus latitude is 0.71 and is significant at the 0.0005 level.Three temporal patterns were recognized among tropical lakes. Most tropical lakes exhibit pronounced seasonal fluctuations that usually correspond with variations in rainfall, river discharges or vertical mixing. A second pattern occurs in lakes with muted fluctuations (coefficient of variation less than 20%) in which diel changes often exceed month to month changes. A third pattern is distinguished by an abrupt change from one persistent algal assemblage (i.e., extant for at least 10 generations) and level of photosynthetic activity to another persistent condition.