Wave forces on intertidal organisms: A case study1

Abstract

Breaking waves impose large forces on intertidal organisms, and these forces are important in structuring wave-swept communities. Here a telemetry system is used to continuously record wave forces at an exposed site; the interpretation of one such record is presented as a case study of the nature of wave forces. For waves with a breaking height of 2-4 m, water velocities of at least 8 m s-l and accelerations of at least 400 m s-~ are present near the substratum. The forces imposed on organisms by these flows depend on the size and shape of the organism. For a limpet (CoZZzkeZIa pelta) an average force is about 0.6 N, a maximum about 3 N. The magnitude and direction of wave forces are unpredictable in both time and space over periods of seconds to hours, although predictability is possible over longer periods. A quantitative exposure index, based on an organism's ability to withstand wave forces, shows that various organisms exposed to the same flow are at widely varying risks. No impact forces were observed during this study.

Differences in feeding adaptations in intertidal and subtidal suspension-feeding gastropods: studies on Crepidula fornicata and Crepipatella peruviana

“…Additionally, abiotic conditions in intertidal and subtidal areas may be nearly identical when the tide is in, and when the tide is out, the suite of abiotic conditions that change is both easily measurable (time emersed, temperature, water lost, etc.) and well characterized (Newell 1979;Denny 1985;Helmuth 1998;Helmuth and Hofmann 2001).…”

“…Species whose populations extend from the intertidal zone (the upper edge of their range) into the adjacent subtidal zone can be studied in the context of range boundaries, but on a much smaller spatial scale. At high tide, intertidal organisms experience many of the same conditions that subtidal organisms do, as the two groups are often only meters apart, and a wellestablished gradient of stressors exists as one moves from the subtidal up through the intertidal zone (Menge 1976;Newell 1979;Denny 1985;Helmuth 1998). Thus, the limiting factors associated with aerial exposure in the intertidal zone and species' adaptations to those factors can be studied by investigating the characteristics of species whose members are living both intertidally and subtidally.…”

Importance of wave and current exposure to fauna communities in Laminaria hyperborea kelp forests

“…The most important factors explaining differences in the community composition were (according to PERMANOVA) habitat morphology, habitat amount, wave exposure and the interaction between morphology and wave exposure. According to Denny (1985), hydrodynamic forces acting on benthos depend on the size and form of the organism, and the significant interaction between waves and algal morphology may have been attributed to differences in the effects that waves impose on different algae as shelter to fauna. There was also some unexplained local variation between the stations.…”

Predicting wave dislodgment of mussels: variation in attachment strength with body size, habitat, and season

“…Intertidal organisms on wave-exposed rocky shores experience large hydrodynamic forces due to breaking waves (Denny 1985, 1995, Denny & Gaines 1990). This water motion has profound effects on many aspects of life on rocky shores, including the supply of food to suspension feeders and of nutrients to macroalgae, the delivery of larvae to the substratum, and the ability of mobile animals to forage for food.…”