A Half Century Assessment of Hard Clam, Mercenaria mercenaria, Growth in Narragansett Bay, Rhode Island

Abstract

During the last several decades, the waters of mid Narragansett Bay, Rhode Island have increased in temperature and decreased in chlorophyll concentration, and it is possible that these changes affected the growth and success of a common benthic filter feeder, the hard clam, Mercenaria mercenaria. We determined recent hard clam growth rates through a sclerochronological analysis and compared them to the rich historical record of Narragansett Bay growth rates in order to understand how these opposing changes influenced hard clam growth. We found no significant differences in short-term growth between 1985 and 2000. Long-term juvenile growth showed a significant decrease between the 1960s and 1990s, while long-term adult (mature) growth showed a significant increase over this same time period. While it is not clear why the changes in juvenile and adult growth rates differ, it appears as though the decrease in chlorophyll concentration, together with a change in phytoplankton community composition, increasing water temperature, and an increase in predator abundance, may all have influenced hard clam growth between the 1960s and the 1990s.

Size-dependent pH effect on calcification in post-larval hard clam Mercenaria spp.

“…We cannot definitively state whether the genotypic differences are responsible for the differences in calcification rates; however, we suggest that determining genotypic effects on calcification rates is an important research avenue that requires further investigation. Extensive work has shown differences in growth rates of natural populations of M. mercenaria with geographic location and other environmental variables (Arnold et al 1991, Carmichael et al 2004, Henry & Nixon 2008, Kraeuter et al 2009). It would therefore be naive to suggest that pH is the only factor that would have significant effects on shell growth in this species and other bivalves, as salinity and temperature also alter calcification (Waldbusser et al 2010).…”

“…The formation of the organic proteinaceous material of the shell occurs at a significant metabolic cost (Palmer 1992), andHautmann (2006) surmised that in thick shelled species, such as hard clams, mineral deposition also required a significant metabolic expense. Considerable attention has been given to growth of adult hard clams (Arnold et al 1991, Carmichael et al 2004, Henry & Nixon 2008 as well as recent work on larval growth of Mercenaria mercenaria and other larval bivalves in relation to pH (Miller et al 2009, Talmage & Gobler 2009). Although some classic works have documented metamorphosis and general growth patterns in the early life stages of M. mercenaria (Carriker 1961(Carriker , 2001 and references therein), little is known about 172 Waldbusser et al: Size-dependent effect of pH on calcification abiotic controls on growth and development in the early post-larval stages.…”

Treatise Online no. 46: Part N, Revised, Volume 1, Chapter 14: Bivalve sclerochronology and geochemistry

“…Temperature exerts the greatest control on shell growth (kenniSh & olSSon, 1975;henry & niXon, 2008). Higher growth rates typically correspond well with higher temperatures.…”

Comparison of Guekensia Demissa Populations Along a Nitrogen Loading Gradient in Narragansett Bay, RI

“…Estuaries have been historically used as transportation and waste disposal, as well as providing coastline area for human development, all which have led to increased nutrient inputs into these bodies of water (Nixon et al 2008). Addition of excess nutrients impacts can affect the entire ecosystem, including primary production levels, dissolved oxygen concentrations, and food web cycles (e.g.…”