Epiphyte-seagrass relationships with an emphasis on the role of micrograzing: A review

Abstract

Despite the recent advances in seagrass ecology over the last ten years, there are still numerous aspects of the ecological and biological interactions that occur in seagrass ecosystems that remain poorly understood. We have attempted, here, to place into perspective one interrelationship that could have important implications in the production and vigor of seagrasses. This is the relationship between epiphytic fouling by macroalgae and periphyton and the grazers which consume them as a food source while leaving the leaves intact. Our approach to this review was first to describe the relationships between macroalgae, periphyton and the seagrass host in terms of physical benefits, biochemical interactions, factors which reduce fouling on the host, and the effects of epiphytism on seagrass photosynthesis. We then examined the importance of epiphytes as a food source for those herbivores found in seagrass beds, and looked at the consequences of this grazing and removal of epiphytes for the seagrass host. Based on the potential impact of epiphytes on seagrass and grazers on epiphytes, we developed a hypothetical model that describes the effect of increasing epiphytic fouling on seagrass production in the presence and absence of grazers. From this model, we have made predictions on the direction of seagrass decline with diminishing light along depth and estuarine gradients. Lastly, we touched briefly on the problem of eutrophication and how it affects the balance of these interrelationships, and the management options to insure the health and survival of seagrass habitats in the face of increasing stress by man on these critically important ecosystems.