The Chemical and Physical Environment

Light photons- packets of electomagnetic energy wavelength: ultraviolet= short; infrared= long ~ 53% of the incident light/radiation is absorbed (transformed into heat) within the 1 st 1M of the water column shorter wavelengths penetrate deeper factors influencing incident radiation: latitude, season, time of day, altitude, & weather conditions

turbidity decreases water’s ability to transmit light –secchi disk –attenuation- reduction of light energy with depth by scattering & absorption

photosynthesis/respiration CO 2 + H 2 O ----> C 6 H 12 O 6 + O 2 radiation nm drives the system

Temperature absorption- the high specific heat of water permits the dissipation of light energy as heat; this process is enhanced by dissolved organic matter. The thermal conductivity of water is low therefore heat radiation is primarily a surface phenomenon.

Metabolic Equilibrium Acclimation- organisms response to environmental change. Immediate response is followed by an adjustment period, then a new steady state.

Regulators vs. Conformers

Thermoregulation Homeotherms- regulate body temperature by reducing convective heat loss. restrictive circulation insulation countercurrent heat exchange

Countercurrent Heat Exchange

Poikilotherms body temperature conforms to that of the ambient environment. metabolic rate increases with temperature subtidal invertebrates and most fish

Temperature Change reduces physiological performance higher temperatures lead to failure of metabolic pathways low temperatures may lead to respiratory depression

Salinity inshore salinities may change rapidly changes affect organisms through processes of diffusion and osmotic balance

Osmotic Balance: Gills

see figure 4.12, p. 90

Oxygen Generally, consumption increases with increased activity. obligate anaerobes facultative anaerobes aerobic