Salinity Debate

First, she found that most searches on alewife reproduction has been conducted on landlocked populations, and hence its application to Oyster Pond is unknown. That being said, alewife eggs have been reported at salinities of 0-3 ppt, while peak larvae abundance has been reported as occurring at either 1-5 ppt or 0-3 ppt, depending on the study. However, other environmental factors also influence egg and larval success, notably temperature. Although most of the literature reports reduced incubation time with increasing temperature, others report an optimal temperature of 20.8 C (69.4 F), with 29.7 C (85.5 F) being lethal for the eggs. Also, alewives lay their eggs in water as shallow as 15 cm: water this shallow would be at the edges of Oyster Pond, where the water may be fresher than the average 2.4 ppt. The combined effects of temperature and salinity are apparently not reported; and of course the temperature of Oyster Pond cannot be controlled in

As far as plant salinity tolerances go, a 2001-2002 study by the Marine Ecology class of B.U.M.P. found that most of the aquatic vegatation in Oyster Pond tolerates a rather broad range of salinity, while species located slightly inland from the pond edge (e.g. rosa rugosa) have lower salinity tolerances. "Ceratophyllum demersum," the coontail species mentioaned above, can survive in salinities ranging from 0 to 6.5 ppt, but it requires a minimum temperature of 20 C (68 F) to grow, as well as high levels of inorganic nitrate: indeed, in 2002, the "C. demersum biomass increased with increasing wastewater nitrogen load..." in Oyster Pond. There is also concern that reducing the salinity of Oyster Pond to 0 ppt (freshwater) could result in a blue-green algae bloom with harmful consequences to the pond's ecological health.

The take-home message from this review of the scientific literature is that many different factors affect the success of fish and plant populations in habitats like Oyster Pond. Clearly, not enough is known about alewife reproduction and submerged weed growth to say with confidence how varying the salinity of Oyster Pond will affect them. Most scientific studies on these topics consider salinity ranges well beyond the narrow range of 0-3 ppt that Oyster Pond usually experiences. The ...

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