Intertidal Landscapes: Disturbance and the Dynamics of Pattern

Abstract

Abstract. The mussel Mytilus californianus is a competitive dominant on wave-swept rocky intertidal shores. Mussel beds may exist as extensive monocultures; more often they are an everchanging mosaic of many species which inhabit wave-generated patches or gaps. This paper describes observations and experiments designed to measure the critical parameters of a model of patch birth and death, and to use the model to predict the spatial structure of mussel beds. Most measurements were made at Tatoosh Island, Washington, USA, from 1970-1979. Patch size ranged at birth from a single mussel to 38 m 2 ; the distribution of patch sizes approximates the lognormal. Birth rates varied seasonally and regionally. At Tatoosh the rate of patch formation varied during six winters from 0.4-5.4% of the mussels removed per month. The disturbance regime during the summer and at two mainland sites was 5-10 times less. Annual disturbance patterns tended to be synchronous within II sites on one face of Tatoosh over a 10-yr interval, and over larger distances (16 km) along the coastline. The pattern was asynchronous, however, among four Tatoosh localities. Patch birth rate, and mean and maximum size at birth can be used as adequate indices of disturbance.Patch disappearance (death) occurs by three mechanisms. Very small patches disappear almost immediately due to a leaning response of the border mussels (0.2 em/d). Intermediate-sized patches ( <3.0 m 2 ) are eventually obliterated by lateral movement of the peripheral mussels: estimates based on 94 experimental patches yield a mean shrinking rate of 0.05 cm/d from each of two principal dimensions. Depth of the adjacent mussel bed accounts for much of the local variation in closing rate. In very large patches, mussels must recruit as larvae from the plankton. Recovery begins at an average patch age of 26 mo; rate of space occupation, primarily due to individual growth, is 2.0-2.5%/mo. ' Winter birth rates suggest a mean turnover time (rotation period) for mussel beds varying from 8.1-34.7 yr, depending on the location. The minimal value is in close agreement with both observed and calculated minimal recovery times.Projections of total patch area, based on the model, are accurate to within 5% of that observed. Using a method for determining the age of patches, based on a growth curve of the barnacle Balanus cariosus, the model permits predictions of the age-size structure of the patch population. The model predicts with excellent resolution the distribution of patch area in relation to time since last disturbance. The most detailed models which include size structure within age categories are inconclusive due to small sample size. Predictions are good for large patches, the major determinants of environmental patterns, but cannot deal adequately with smaller patches because of stochastic effects.Colonization data are given in relation to patch age, size and intertidal position. We suggest that the reproductive season of certain long-lived, patch-dependent species is moulded by the distu...

Movements of Marine Fish and Decapod Crustaceans: Process, Theory and Application

“…Valuable early contributions to the conceptualisation of ecological systems as "dynamic mosaics of patches" took place in benthic and pelagic marine environments (e.g. Levin and Paine, 1974;Steele, 1978;Paine and Levin, 1981;Sousa, 1984;. It is in terrestrial environments, however, that the quantification of landscape pattern and the study of the effect of pattern on ecological processes have made significant advances in understanding animal movement and persistence, the effects of disturbance, the importance of broad-scale environmental change and the design of resource management strategies (Turner, 1989;Saunders et al, 1991;Hobbs, 1994;Forman, 1995;Farina, 1998).…”

Formation and disruption of aggregations of Mytilus edulis in the fouling community of San Francisco Bay, California

“…While this study and several others (Paine & Levin 1981, Schoener & Schoener 1981 imply that edge effects may influence rates of succession to the competitive dominant, the importance of edge effects to successional dynamics has received little investigation. It is clear that to gain a n understanding of patch dynamics in a number of systems it may b e necessary to subdivide our scales of observation a n d to study areas of habitat in finer detail.…”

“…Keen & Neill 1980, Russ 1980, Chalmer 1982, however organisms can respond differentially to patches of habitat and thereby may exert potentially important 'edge effects'. Edge effects can result from patterns in the settlement of organisms (Bernstein & Jung 1979, Schoener & Schoener 1981, this study), and they have been shown to arise through the action of grazers in a number of systems (Randall 1965, Bartholomew 1970, Dayton 1971, Ogden et al 1973, Stimson 1973, Suchanek 1978, Paine & Levin 1981, Sousa 1984.…”

“…Patterns of succession in the rocky intertidal of the Pacific Northwest have been extensively investigated (Dayton 1971, Paine 1974, Paine & Levin 1981. In this system the mussel Mytilus californianus is the dominant competitor for space and forms extensive beds.…”

Self-thinning and community persistence in a simple size-structured dynamical model of plant growth

“…which has been used by many authors in plant ecology (Nagano, 1978;Takada and Iwasa, 1986;Kohyama, 1992) as well as in various other fields of biology (Trucco, 1965;Shinko and Streifer, 1967;Levin and Paine, 1974;Paine and Levin, 1981;Kirkpatrick, 1984). Likewise, the Sharpe-Lotka-McKendrick-von Foerster equation is a particular version of the more general Fokker-Plank equation (also known as diffusion or Kolmogorov forward equation), which describes the moment dynamics of a probability distribution and has been used by Hara (1984b) and many others to incorporate the spatial and stochastic fluctuations of the size density distribution.…”