Comparison of Lake Biwa and Great Lakes on the Functions of Littoral Zone

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The horizontal distribution of water level, current, temperature, electric conductivity and turbidity were measured in wetland in Lake Huron's Saginaw bay.During summer, remarkable gradients of water quality existed on transect perpendicular to the coast line. Nearshore water was clean with high conductivity, while water in offshore portions of the wetland was turbid and had low conductivity. Large amplitude water level changes occurred commonly in the wetland. The cycle of one such change had a period of approximately 24 hrs, and another a period of about 3 hrs.The former were caused by daily changes in the direction of breezes blowing from the land and from the bay. The latter resulted from transverse surface seiche in the bay.Water level changes influenced spatial distribution of water quality in the wetland ; that is, the front between clear nearshore water and tubed offshore water moved inward and outward from shore as water level rose and fell respectively.Currents associated wit … More h rise and fall of water level ran perpendicular to shore and were generally very weak (2-3 cm/sec).Emergent wetlands dominated by the bulrush Scripus americanus are common in the shore zone of Saginaw Bay. Chlorophyll a concentration from algae in the periphyton community on shoots of Scirpus americanus were significantly higher per shoot and per unit area of shoot surface in offshore portions of the wetland than in nearshore portions. Gross primary productivity of periphytic algae per shoot and per unit area of epiphytic chlorophyll a was highest further from the shore.During summer, dense bulrush shoot impede mixing of water between nearshore and offshore portions of the wetland. Anoxic conditions associated with decomposition of dead vegetation existed in nearshore water, particularly in early morning.Low sulfate concentrations were present in nearshore water as compared to water in offshore portion of the wetland. This difference was caused by reduction of sulfate under anoxic nearshore conditions. Nearshore water also had high concentrations of Mg++, Na+, and cl- and other ions as compared to water in offshore portions of the wetland. Evaporation and transpiration losses from shallow nearshore water, and absence of mixing of nearshore water with water from the bay as occurred in offshore portions of wetland, may have caused these differences. Less