Importance of predatory infauna in marine soft-sediment communities

Abstract

Ambrose (1984a) suggested that a 3-way interactive model should be applied to marine infaunal communities having the levels of epibenttuc predators, predatory infauna and nonpredatory infauna. It is shown that the 3-level interactive model incorporates the implicit, unstated assumption that epibenthlc predators preferentially prey on predatory infauna. A review of the literature reveals that this assumption is not true. The assumption of predatory infauna being more susceptible to epibenthic predation is challenged. Reanalysis of the caging studies analyzed by Ambrose with a more ngorous and conservative classification of predatory and nonpredatory lnfauna provides no support for the proposed model. The application of the proposed 3-level interactive model to marine infaunal communities is not justified.

Guild structure and foraging impact of blue crabs and epibenthic fish in a sub-estuary of Chesapeake Bay

“…Third, as consumers of infaunal predatory worms, variation in the abundance of fish in the guild alters the ratio of infaunal predators to infaunal prey. Although the validity of these altered ratios is open to question (see Ambrose 1984, Wilson 1986), the shifts in ratios that we observed in the predator exclusion experiment indicate that nonlinear effects on community structure occur with variation in fish predation intensity. In areas of inherently low diversity like the upper reaches of estuaries, these shifts in species composition may be of considerable consequence.…”

“…mean abundances of each dependent variable (log abundance of each infaunal species) were tested for differences among cage treatments at each of the 5 stations using Tukey's simultaneous test for unplanned multiple comparison of means with unequal sample sizes (see Day & Quinn 1989) as modified by Cicchetti (1972) to avoid confounde d comparisons. To test whether re duction in predation pressure by epibenthic fish and crabs enhanced infaunal predatory versus non-predatory species (see Ambrose 1984, Wilson 1986). differences in the ratio of infaunal predators (Nereis succinea + Eteone h eteropoda x Carinoma tremaphorus) to infaunal prey (sum of other species) among treatments, stations, and their interaction were tested by ANOV A after Fmax tests of arcsine-squareroot transformed data indicated homogeneity of data.…”

Importance of predatory infauna in marine soft-bottom communities: reply to Wilson

“…I initially tested this model by comparing the ratio of the abundance of predatory infauna to nonpredatory infauna in the presence and absence of epibenthic predators and found that the ratio Increased as predicted following the removal of epibenthic predators. Wilson (1986) demonstrates that preferential predation on predatory infauna by epibenthic predators is a requirement of the 3-level model, but finds no support for such predation in the literature. Wilson also reanalyzes the data set I used to test my model using a different definition of predatory infauna and finds no significant difference in the ratio of predatory infauna to non-predatory infauna between caged and uncaged areas.…”

“…By modeling the effects of preferential and nonpreferential predation on the ratio of predatory infauna to non-predatory infauna, Wilson (1986) shows that the 3-level model depends on preferential predation. Wilson's model, however, is inexact because it does not use a continuous function to analyze changes in the ratio of predatory to non-predatory infauna.…”

Differential regulatory roles of crustacean predators in a sub-arctic, soft-sediment system

“…crabs, shrimps, fishes) and infaunal prey, and instead proposed an additional 'predatory infauna' level that mediates the interactions between top epibenthic and non-predatory infauna. Wilson (1986) questioned this view, arguing that in order to verify the existence of such trophic complexity in soft sediments, top (epibenthic) predators should display strong preference for predatory infaunal species. Our design was not intended to resolve this debate, but using Wilson's arguments, our results clearly support the view of Ambrose (1984): P. tecta was several times more abundant in exclusion than in predator treatments, both in field and in laboratory experiments.…”