STRESS TOLERANCE IN INTERTIDAL SEAWEEDS

Intertidal seaweeds are periodically exposed to air where they experie nce a variety of potentially stressful environmental conditions, inclu ding nutrient limitation, high Eight, high and low temperature, desicc ation, and osmotic stress. This paper considers the current understand ing of stress tolerance in intertidal seaweeds and discusses ways in. which future research could increase our understanding of the role of environmental factors in the ecology and physiology of these algae. We believe research is required in at least three areas. 1) Laboratory p hysiological studies have established that correlations exist between stress tolerance and the vertical distribution of species. However, li ttle information is available on the importance of stress in determini ng community structure in nature. Field experiments are essential to r ebate the impact of single or multiple stresses on the survival, growt h, and reproductive output of macroalgae. In particular, it is necessa ry to clarify, the role of sublethal stress in determining the outcome of competitive interactions. 2) With the exception of obvious lethal effects or damage associated with extreme environmental conditions, su ch as unusually hot and dry weather, it is difficult to evaluate the o ccurrence and severity of stress in natural populations of seaweeds. T here is a need to develop molecular and biochemical markers specific f or individual stresses or groups of stresses to allow the unambiguous and direct determination of stress in situ. 3) Despite the apparent im portance of stress in intertidal seaweeds, we are largely ignorant of the mechanistic basis of tolerance. The application of currently avail able tools of molecular and cell biology to the investigation of stres s-induced transcriptional and translational changes could enormously i ncrease our understanding of both the sites of, and pathways involved in, stress tolerance. In summary, there are numerous unanswered fundam ental questions about the stress tolerance of intertidal seaweeds, pro viding opportunities for research ranging from field ecology to molecu lar biology and biochemistry.