Estimating potential diapause duration in Calanus finmarchicus

Deep basins in the Gulf of Maine act as refuge for a large population of diapausing Calanus finmarchicus during the summer and fall. This population acts as the primary seed population for Georges Bank in the spring and is thought to be composed primarily of individuals that developed during the previous spring bloom. The factors affecting growth and mortality in the summer-fall population are not well understood, however, and loss terms from advection and starvation may be large. To assess the potential energetic limitation and loss of C. finmarchicus from the Gulf of Maine basins, a new nitrogen-specific respiration model has been developed for the resting stage of the species. Stage C5 C. finmarchicus were collected during July, September, and December 2003 from Wilkinson and Georges Basins. Animals were collected using both MOCNESS tows and zooplankton samplers on the Johnson Sea Link II submersible. Metabolic rates were measured using a Micro-Oxymax gas analyzer and Winkler incubation techniques both at sea and on animals kept in culture on shore. Respiration rates measured in the field were not significantly different from those measured on shore, with a mean of 130 μmol O2 gN-1 h-1 (14.4 μmol O2 gC-1 h-1) at 0 °C and a Q10 of 2.77 (2.58 for carbon-specific respiration). Using the nitrogen-specific rates in conjunction with visual estimates of nitrogen weight and lipid stores, we derived a discrete function for predicting potential diapause duration based on an animal\u27s length, oil sac volume, and the in situ temperature. The maximum potential diapause duration for a C5 C. finmarchicus is predicted to range from 280 days at 0 °C to approximately 90 days at 11 °C. The maximum potential diapause duration in the Gulf of Maine is predicted to be between 3.5 and 5.5 months. These results suggest that energetic limitation may play a role in controlling the population dynamics of diapausing C. finmarchicus in the Gulf of Maine. A reassessment of the importance of summer production to the Gulf of Maine C. finmarchicus population may be required to account for its year-round presence on the Northeast American Shelf. © 2006 Elsevier Ltd. All rights reserved

The impact of increasing temperatures on dormancy duration in Calanus finmarchicus

Dormancy is a key life history trait of planktonic calanoid copepods in the genus Calanus. Empirical evidence suggests that duration of dormancy is controlled by ambient temperature driving lipid metabolism in individuals. Here, we use the temperature-dependent metabolic rates of overwintering individuals to show that increasing temperatures, associated with global climate change over the next several decades, may reduce dormancy duration for the north Atlantic species C. finmarchicus by up to 40 days. Our calculations are based on comparing predicted dormancy duration for individuals of a given size at specific temperatures to dormancy duration at warmer temperatures and smaller size. We also provide corrections to the relationship of dormancy duration described by Saumweber and Durbin [Estimating potential diapause duration in Calanus finmarchicus. Deep Sea Res. Pt. II., 53, 2597–2617.]. Our calculations indicate that changing temperatures in the sea may lead to phenological shifts in life histories of C. finmarchicus and congeners, which may have implications for planktonic food web and trophic dynamics.Keywords: Life history, Calanus finmarchicus, Dormancy, Climat

Safe Harbors: The Many Benefits of Marine Monuments and Sanctuaries

The United States has been at the forefront of marine resource stewardship since the 1970s when Federal officials began to implement a series of national policies aimed at the conservation and management of public trust resources in the ocean. Beginning with the establishment of the National Oceanic and Atmospheric Administration in 1970, soon followed by several pieces of landmark legislation, this era marked the start of a continuing effort to integrate ecosystem science with marine resource management. Among the most important bipartisan legacies of this effort has been the steady expansion of marine managed areas in U.S. coastal and ocean waters. This legacy is being challenged as the Trump Administration considers whether to alter or eliminate the nation's Marine National Monuments and National Marine Sanctuaries