Wave energy and intertidal productivity

Abstract

In the northeastern Pacific, intertidal zones of the most wave-beaten shores receive more energy from breaking waves than from the sun. Despite severe mortality from winter storms, communities at some wave-beaten sites produce an extraordinary quantity of dry matter per unit area of shore per year. At wave-beaten sites of Tatoosh Island, WA, sea palms, Postelsia palmaeformis, can produce >10 kg of dry matter, or 1.5 x 108 J. per m2 in a good year. Extraordinarily productive organisms such as Postelsia are restricted to wavebeaten sites. Intertidal organisms cannot transform wave energy into chemical energy, as photosynthetic plants transform solar energy, nor can intertidal organisms "harness" wave energy. Nonetheless, wave energy enhances the productivity of intertidal organisms. On exposed shores, waves increase the capacity of resident algae to acquire nutrients and use sunlight, augment the competitive ability of productive organisms, and protect intertidal residents by knocking away their enemies or preventing them from feeding.

Nutrient loading and consumers: Agents of change in open-coast macrophyte assemblages

“…Although it is common knowledge that fertilizer will help a garden grow or a lake to bloom, many littoral fringe ecologists have not considered nutrient limitation possible in open-coast benthic macrophyte assemblages, especially in upwelling ecosystems (24). The dramatic changes in the structure of an intertidal macrophyte assemblage as a result of relatively small changes in nutrient supply documented here suggest that open-coast marine communities are more sensitive to fluctuations in nutrient regimes than previously appreciated.…”

“…The striking convergence of community structure in these two treatments strongly suggests that variation in nutrient mass transfer rates contributes to variation in the structure of intertidal macrophyte assemblages across wave exposure gradients. Additional factors that contribute to variation in the structure of macrophyte assemblages over wave exposure gradients include: (i) reduced herbivore biomass and efficiency (46,47) and (ii) increased light utilization efficiency of kelps with increasing wave exposure (24,48).…”

Contingencies and compounded rare perturbations dictate sudden distributional shifts during periods of gradual climate change

“…Our survey site is on a very wave-exposed promontory, which may make it especially vulnerable to calm weather as the M. parksii zone is above the extreme high tide line (15). However, even lower shore populations would be vulnerable to stressful air temperatures during low tides and during periods of neap high tides.…”

“…Waves have the potential to interrupt stress events by rehydrating organisms and by resetting body temperatures to that of sea water (14). Thus, the upper limits of sessile species, including M. parksii, are generally higher on the shore in areas of increasing wave exposure (14)(15)(16).…”

Evaluation of effective shore level as a method of characterizing intertidal wave exposure regimes

“…Yet attempts to generalize such local zonation schemes to larger regions are frequently unsuccessful (Stephenson and Stephenson 1972). There is often great disparity in zonation patterns among locations or within a location over time (Lawson 1957, Paine 1966, Leigh et al 1987, Foster 1990.…”