Temperature and Desiccation

stratification

warm water sits on top of cold water and prevents nutrients from getting to surface

the tropics have a thermocline

permanent

the poles have a thermocline

nonexistent; seasonal peak of primary productivity

the temperate latitudes have a thermocline

seasonal

marine heat waves

surface temperatures are higher than the local threshold for 5+ days 

why do marine heat waves occur?

increased co2 emissions warm the water

indirect impacts of marine heat waves

food availability, currents, species interactions

direct impacts of marine heat waves

species range shifts, increased metabolic rate and cellular stress in organisms

the blob

longest marine heatwave (2013-2016) due to suppressed heat loss and reduced winds due to high atmospheric pressure

impacts of the blob

fisheries collapsed due to mass mortality of marine species and changed migration patterns

intertidal temperatures

extremely variable

effects of high temperature

protein denaturation, disturbed membrane function, high energy costs, desiccation, ionic imbalance

protein denaturation

bonds between proteins break down and the protein loses its shape and enzymes stop working

homeotherms

maintain constant body temperature; mammals and birds

ectotherms

temperature impacts metabolic rate; invertebrates, plants, most fish

method to reduce heat gain

reduce body tissue in contact with substrate

method to increase heat loss

ridged shells to increase surface area, extra water supply for cooling, hiding, rhythmic phototaxis

black shells

gain and lose heat faster

light shells

cooler for longer but longer to heat up

heat shock proteins

prevent protein damage, refold damaged proteins, maintain membrane function

how are heat shock proteins produced?

heat shock factors dissociate from carriers and turn on heat shock genes

behavioral adaptations to prevent desiccation

circatidal migration, shielding, attaching to moist/shaded areas, reduced urine output, store waste as uric acid, water reserve in mantle cavity

biochemical adaptations to prevent desiccation

wide range of tolerance, shut down biochemical processes at extremes

morphological adaptations to prevent desiccation

shells (mucus, direction, color, operculum, ridges)

physiological adaptations to prevent desiccation

modified/protected respiratory organs, small o2 uptake

cryoprotectants

reduce ice content in tissues by lowering freezing point

osmolytes

compounds that regulate osmotic stress and cellular homeostasis

ice binding proteins

proteins bindable to ice in gastropods and bivalves; thermal hysteresis, ice recrystallization inhibition, ice nucleation

thermal hysteresis

prevent ice formation by altering melting and freezing points

supercooling

maintain liquid internal conditions below freezing point

countercurrent heat exchange

uninsulated appendages, loop blood (heat) back through core before extremities, maintain metabolic heat

glycoproteins

prevent ice lattice from forming in fish