Invertebrate Aquaculture in a Changing Global Environment

Project Description

Project personnel are assessing the effects of increasing ocean temperatures and acidification on calciferous invertebrates to understand how environmental changes can alter the health and physiology of aquaculture species. Many of the physiological measurements and assessments are hampered by small sizes. Researchers are using the American lobster as a calciferous decapod standard model organism because they grow rapidly, are large at metamorphosis, and information on their genome is readily available.

Temperature studies investigated the effects of three temperature regimes on survival, growth, morphometrics, shell microstructure, hemolymph protein, and gene expression in newly metamorphosed (stage four) lobsters exposed to these regimes since hatch.

Ocean acidification studies investigate the effects of an acidified environment on sub-adult lobsters, and will examine the ecdysteroid hormone as well as transcriptomic changes in the hepatopancreas of sub-adult lobsters exposed to the acidified environments for a period of 60 days. A subset of animals from the ocean acidification (OA) study have been used in a temperature ramping study.

Results and Accomplishments

Project personnel examined how ocean temperatures (14, 16, 18 and 22°C) impact growth, survival, and measures of immune health such as hemocyte abundance and developmental stability. Hemocytes are cells that are carried in the lobster’s circulating fluid, called hemolymph, that attack foreign invaders through phagocytosis and other mechanisms. Developmental stability was measured via fluctuating asymmetry, which is defined as random deviations of bilateral traits from perfect symmetry due to subtle variations in the developmental environment. This is a common metric of developmental stability in other taxa, and can be influenced by environmental stressors, including temperature.

Project personnel found that elevated temperature accelerated development, and generally increased survival. However, hemocytes were elevated at the temperature extremes, which is indicative of increased physiological stress. Midline asymmetry was significantly lower at the temperature extremes, which may be due to the survival of the select individuals with genotypes tolerant of thermal stress. This also suggests that postlarval populations reared under the warmest temperatures may have lower adaptive capacity for additional stress. This is particularly important in the context of climate change, in which post-larvae will have to deal with numerous other stressors in addition to warming temperatures. Taken together, these data indicate a potential tradeoff between enhanced growth and sub-lethal impacts on larval physiology under warming conditions. This study highlights the utility of fluctuating asymmetry as an indicator of developmental stability.

Summary of Data Being Collected

Data Type Quantity Location
Survival Physiological >200 Aquaculture Research Center, UMaine
Morphometrics Physiological >200 Aquaculture Research Center, UMaine
Other physiological parameters (hemolymph protein, shell microstructure, hemocyte counts) Physiological >100 Aquaculture Research Center, UMaine
Transcriptomics Molecular 30 Contract lab
Temperature ramping Physiological 10 Aquaculture Research Center, UMaine