BIODIVERSITY OF MARINE PLANTS IN AN ERA OF CLIMATE-CHANGE - SOME PREDICTIONS BASED ON PHYSIOLOGICAL PERFORMANCE

There are too few data to allow any confident statements on the effect s of global climate change on the diversity of marine plant life. Howe ver, on the basis of information available in the literature, it is po ssible to make predictions about the physiological responses of plants under situations of anticipated increases in CO2 concentrations, temp erature and UV-B fluxes and point out how differences in the responses of major marine plant groups might lead to changes in performance and distribution of these organisms. For instance we may predict that mac rophytes such as seagrasses will show enhanced photosynthetic rates an d growth as atmospheric CO2 levels continue to rise whilst many intert idal macroalgae are already at CO2 saturation and may not show any enh anced performance as CO2 increases. Decreasing ozone concentrations in the stratosphere will lead to enhanced UV-B fluxes and could conseque ntly favour those species with UV tolerance or repair mechanisms. It h as been suggested that interactions between temperature range and phot operiod can be responsible for excluding species from particular regio ns of the world's oceans. Other species might be affected in this way as temperatures at a given latitude change. Temperature will also infl uence the relationship between atmospheric and dissolved CO2 and the p roportions of the various components of dissolved inorganic carbon ava ilable for growth. Climate change may well have other effects on the e fficiency with which marine plants use other resources such as N, Fe o r Zn and these will also be discussed.