The thermal window for aerobic scope in shallow water marine invertebrates.

Main area:Marine biology
Target group:Biology
Educational level:Bachelor, Masters
Project description:

The energy metabolism supports the processes that animals need in order to function. It can be determined by measurement of respiration rate (i.e., oxygen used per time unit). The “standard metabolic rate” (SMR) is defined as the minimal rate of energy expenditure per unit time (i.e., resting and no active digestion). The SMR in Poikilothermic animals, such as marine invertebrates, are affected by the temperature of the surrounding water. The effect of temperature follows a power function (Q10) and normally the SMR doubles - triples when temperature is increased with 10 °C (i.e., Q10 = 2 - 3). The “maximum metabolic rate” (MMR) is defined as the energy expenditure per unit time that an animal can achieve at a given temperature under any ecologically relevant circumstance. The effect of temperature on MMR follows a parabolic function. At any given temperature subtracting the MMR from the SMR gives the metabolic rate an animal has available for other functions than the SMR. This is called the aerobic scope (AS). At the temperatures were the SMR and the MMR are equal the aerobic scope is zero and the temperatures at which this occur is called the critical temperature (Tcrit). The temperature at which the aerobic scope is largest is termed the optimal temperature (Topt). Finally, the thermal window is defined as the temperature range between the two critical temperatures. Outside this window animals will have no available energy for anything else than SMR and they will die if kept outside the window for a prolonged period of time.

The thermal window for aerobic scope has been extensively studied in fish. However, such studies are very scares when it comes to marine invertebrates. One challenge is that the MMR determination includes a protocol where the test animal is chased in order to achieve its MMR. Of course several invertebrate species can be chased (e.g., mobile crustaceans) but for many invertebrate species this is not possible. For example how do you chase a blue mussel? One bivalve species actually allows for a chase protocol. Scallops are able to swim and will do so if an approaching sea star is detected. This offers the possibility to perform a chase protocol and thereby allowing the MMR to be determined. Another method has been applied for bivalves which can not be chased. In this method, the MMR determination is substituted with the oxygen consumption of the bivalve feeding at its maximal rate. This is called the active metabolic rate (AMR). The aim of the project is to get information on the thermal window for aerobic scope of marine invertebrates. Dependent on the invertebrate species chosen the study can be directed towards global warming issues.

Methods used:Computer controlled intermittent respirometry.
Keywords:Marine bivalves and or crustaceans, physiology, respirometry, global warming.
Supervisor(s):  Bent Vismann