Relationship between cover of Chondrus crispus (Gigartinales, Rhodophyta) and Phymatolithon (Corallinales, Rhodophyta) on friable rock substrata

Abstract

Field observations in sublittoral Prince Edward Island, Canada, indicated that on a friable sandstone substratum Chondrus crispus was more commonly associated with Phymatolithon sp . than with bare rock . Thus, a substantial proportion of the population of Irish moss along the coast of Prince Edward Island occurs on this encrusting coralline . These observation may be explained on the basis of the relative stability of the substratum in contrast to other studies in which sloughing of epithallial cells by species of both Phymatolithon and Lithothamnium has been reported to limit epiphytism by fleshy macrophytes .

Effects of Disturbance, Life Histories, and Overgrowth on Coexistence of Algal Crusts and Turfs

“…Regardless of different roles attributed to competition and disturbance, most of the classical models assume that primary space is a potentially limiting resource and explain coexistence as a consequence of processes allowing its partitioning among species (Dayton 1971, Yodzis 1978, Buss and Jackson 1979, Sousa 1979, Paine 1984, Pickett and White 1985. The results of the present study and other studies, however, indicate that overgrowth is not always equivalent to competitive displacement, and that tolerance may allow long-term spatial overlapping among species (Rutzler 1970, Sara 1970, Osman and Haugsness 1981, Miles and Meslow 1990, Parker and McLachlan 1990. Thus, use of secondary substrata may be a determinant in maintaining spatial coexistence between species (Lee andAmbrose 1989, Lohse 1993).…”

“…For this reason, encrusting algae are widely considered as subordinate to algae of other morphologies in the hierarchy of ability to compete for space (Littler and Littler 1980, Breitburg 1984, Dethier 1994, Steneck and Dethier 1994, but see Underwood 1980 andPadilla 1984). This supposed competitive inferiority contrasts with the evidence that encrusting algae are among the major holders of primary hard substrata in marine habitats within the euphotic zone (Littler 1972, Adey and Macintyre 1973, Steneck 1986, Dethier 1994, Kaehler and Williams 1997 and that they often coexist with their epiphytes (Miles and Meslow 1990, Parker and McLachlan 1990, Figueiredo 1997. This would suggest that the common interpretation of competitive ranking based on the ability to overgrow may not be adequate to explain patterns of distribution of encrusting algae and their interactions with other species.…”

“…Encrusting algae and filamentous turfs often occur together in different habitats (Parker and McLachlan 1990, Williams and Carpenter 1990, Kendrick 1991, Airoldi et al 1995, Figueiredo 1997, but the mechanisms that allow the persistent coexistence of these two growth forms have received little attention. I use Welden and Slauson's (1986:25) definition of competition, i.e., "the induction of strain in one organism as a result of the use, defense, or sequestering of resource items by another organism," where strain is a "deleterious, suboptimal physiological state" that is sometimes translated "into mea- surably reduced growth rate, size, or reproduction, or into increased mortality or emigration and thus into reduced fitness."…”

The settlement, attachment and establishment of marine algal spores

“…It is particularly well known that friable rocks offer poor substrata for algal growth. For example, McLachlan et al (1987) refer to the absence of a stable canopy of laminarians on friable sandstone, Parker & McLachlan (1990) refer to Phymatolithon stabilizing the rock surface and allowing Chondrus populations to recruit whilst refer to magnesium limestone stones as being too friable for Himanthalia establishment. There is also some evidence that different rock types can influence the development and adhesive properties of the attachment cells/ rhizoids.…”

Transition probabilities help identify putative drivers of community change in complex systems

“…). Red algae and encrusting coralline often covary and codominate in intertidal communities (Parker and McLachlan ) because they tolerate overgrowth by each other, and reach stable competitive equilibria (Airoldi ). Further, though encrusting coralline may provide settlement surface for other species (Elahi and Sebens ), red algae and encrusting coralline codominance persists since limpet grazers preferentially recruit to encrusting coralline (Steneck ) and physically scour epibionts other than red algae (Lubchenco and Menge ).…”