Studying mesoalgal structures: A non-destructive approach based on confocal laser scanning microscopy

Abstract

Mesoalgae play a key role in shallow coastal ecosystems. Composed of small macroalgae, intermixed with filamentous cyanobacteria and colonial diatoms, these multi-specific, but minute (μm-cm) assemblages form complex three-dimensional structures, providing shelter for different unicellular (e.g. bacteria, diatoms, dinoflagellates) and multicellular (e.g. fishes, invertebrates) organisms. Characterized by a high colonization potential, these primary producers are observed to bloom and overgrow disturbed areas (e.g. damaged coral reefs, urchin barrens), and play a crucial role in terms of invasion and colonizing new habitats. Driven by anthropogenic environmental changes, mesoalgae are receiving considerable attention in current marine research. So far, most studies approach mesoalgae at the functional group level (e.g. turf algae, microphytobenthos), whereas only few studies tackle the importance of species-specific interactions, which play an important role in benthic ecology (e.g. coral-algal competition and disease spreading). To facilitate the study of not only the presence but also the composition and the structure of these habitat formers, we provide a new approach combining inexpensive fixation methodology with modern confocal laser scanning microscopy (CLSM), to study minute macroalgal structures (e.g. germlings, reproductive structures), and investigate their relation to microphytobenthic components (e.g. diatom colonies). Detailed procedures for mounting, staining and imaging phytobenthic communities are provided.