Biomass Turnover, Respiration, and Interpopulation Variation in the Stream Limpet Ferrissia rivularis (Say)

Abstract

The stream limpet Ferrissia rivularis, which occurs extensively in North America and is ubiquitous in streams of upper New York State, was studied from two distinct populations, one located in the Canandaigua Outlet at Alloway, N. Y. (AL) and the other in Black Creek at Cleveland, N. Y. (BC). These environments differ substantially, that at AL being the more eutrophic. At BC there is one generation per year, but at AL there are two generations per year and more rapid growth rates. Thirteen months is the adult life span for BC limpets, whereas at AL 11 and 3 months are normal for spring and summer adults respectively. At BC 8.4 eggs per limpet are laid, and 34.8 eggs per limpet are laid by spring adults at AL. Biomass and egg production are assessed as total carbon (equivalent to calorific measures) and expressed as biomass—turnover rates (growth and egg production). Egg—production rates can be double those for growth at AL; at BC egg—production rates are usually less than those for growth. This is partly a consequence of greater primary productivity at AL, but may also reflect implied genetic differences. Limpets at BC build up carbon during late summer and early fall; an increase in the C:N ratio (to 4.8) indicates an accumulation of storage compounds. During the winter (lower temperature, solar input, and primary productivity) the C:N ratio decreases, and during spring breeding there is a more marked loss of carbon associated with egg laying. In field—acclimated BC animals, respiration is lowest during the winter; during the spring, respiratory rate is closely correlated with temperature and egg—laying intensity. Oxygen—consumption measurements at 10° and 20°C for all seasons reveal that these limpets show reverse acclimation at low temperature (qualitative and quantitative downward adjustment of metabolism). This acclimation pattern is accompanied by a decrease in Q10 (3.3 to 2.1) which can act to dampen the effects of winter temperature fluctuations. Energy balance (respiration, growth, egg production) is expressed as rates of carbon turnover for the population at BC. Respiration rates are greatest during the summer and spring and reflect increased assimilation due to growth or reproduction or both. The total carbon turnover per year is approximately 1.25 g/m2. Data on energy balance emphasize the adaptive importance of reverse acclimation at times of low energy input.