الفهرس | Only 14 pages are availabe for public view |
Abstract The transitional systems located between land and open sea, i.e . .estuaries, bays and coastal marine areas are often subjected to the discharge of treated and untreated waste waters rich in organic substances, agricultural and industrial wastes. The land runoff affects the marine processes that alter the natural dynamic equilibria and the biotic composition of the respective ecosystems, leading to increased production of phytoplankton, development of visible algal blooms and abnormalgrowth of submerged attached and/or floating algal mats. Changes in phytoplnkton standing crop, community structure and species composition are driven by a mixture of autogenic processes such as competition for light (Parsons, 1979), nutrients (Harrison et aI., 1981; Takahashi & Fukazawa, 1982) and allogenic as temperature (Goldman & Ryther, 1976), and salinity (Smayda, 1980). Grazing (Harrison et al., 1983) and sinking rate (Smayda, 1970) are also factors that influence phytop1ankton standing crop. However, it is difficult to establish quantitatively the extent of their effects because of the variability in the environmental gradients in situ (Mukai & Takimoto, 1985) and the different response of the different species to changes in the surrounding environment (Richmond, 1986). Stability of water column is an important factor controlling phytoplankton standing crop and seasonal succession (Pingree et al., 1976; Holligan & Harbour, 1977; Raymont, 1980), in controlling mixing and hence to a great extent the availability of light energy and nutrients for phytoplankton growth (Pingree et al., 1978). Margalef (1978) and Bowman et al. (1981) have related dominant phytoplankton life-forms in marine environments with the input of external energy manifested as water movement. |