Population dynamics and seasonal lipid cycles in hyperbenthic crustaceans from a cold-ocean environment (Conception Bay, Newfoundland): Mysis mixta (Mysidacea) and Acanthostepheia malmgreni (Amphipoda)

• Main Author: Richoux, Nicole Bertine
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2004
• Subjects: Newfoundland
• Online Access: https://research.library.mun.ca/11339/; https://research.library.mun.ca/11339/1/Richoux_NicoleB.pdf

Life cycles and seasonal changes in density, biomass, growth, secondary production and lipids in Mysis mixta and Acanthostepheia malmgreni from a 240-m deep site in Conception Bay, Newfoundland, were studied from October 1998 to November 2000. The primary aim was to provide life-history and ecological information on populations inhabiting the hyperbenthos of Conception Bay, and to relate the seasonal lipid and fatty acid dynamics to each species' life cycle and to the occurrence and quality of the annual phytoplankton bloom. -- Life spans and reproductive cycles were remarkably similar in the two species, with the release of free-living juveniles from mature females occurring in April and May when bloom material was settling to the hyperbenthos. Females reproduced once and then died at age-2.5 years following a 5-month brooding period of larval stages. The biennial life cycles of both populations resulted in the presence of 2 cohorts of each species co-existing at most times, although a marked annual alternation in cohort dominance occurred in the amphipod population. Annual production:biomass (P/B) ratios in the mysid population were similar in both years, indicating consistent recruitment from year to year. In contrast, the alternation in cohort strength in A. malmgreni had significant repercussions in the success of this population, reflected in a lower P/B ratio in 1999 than in 2000. -- Divergent patterns in lipids, fatty acids, and specific fatty acid marker ratios reflected differing life styles, diets and critical periods of energy accumulation and utilisation in M. mixta and A. malmgreni . Influenced by the seasonally productive and perpetually cold environment created by the Labrador Current, M. mixta and A. malmgreni both accumulated high levels of lipid reserves similar to those attained by other cold-water zooplankton. Maximum lipid stores were observed in females, although the maximum lipid content in M. mixta was over twice that in A. malmgreni. Lipid levels increased with maturity, and developing ...