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.

Anthropogenically driven habitat formation by a tube dwelling diatom on the Northern Patagonian Atlantic coast

“…In the laboratory, the substrates and algal material were mounted in semi-permanent slides (SLIDEs) using a corn syrup (Karo TM light) solution, diluted with distilled water (1:1) and few drops of 4% formaldehyde to avoid bacterial and fungal growth. Material selected to CLSM analyses was remounted and stained with Congo Red following the protocol of Fricke et al (2017).…”

Tropical bloom‐forming mesoalgae Cladophoropsis sp. and Laurencia sp.—responses to ammonium enrichment and a simulated heatwave

“…Next to different conspicuous bloom-forming macroalgal genera like Sargassum, Gracilaria, or Ulva, there are a number of reports on blooming, somewhat cryptic taxa (Fricke et al, 2017;Littler et al, 2010;Lovelock et al, 2008;Vermeij et al, 2010). These socalled mesoalgae, a term first introduced by Fricke et al (2017), bridge the classical size-related terms macroalgae (visible by naked eye) and microalgae (visible under a microscope), and the term refers to all macroscopically visible algal elements (e.g., tufts, turfs, mats, and crusts), which can hardly be determined on a generic level without a microscope (Fricke et al, 2017;Juráň & Kaštovský, 2019). In this respect, mesoalgae can comprise different minute macroalgal stages (e.g., propagules, germlings, uniseriate, and fine filamentous thalli), as well as dense-growing colonies of microalgae (e.g., cyanobacteria and diatoms).…”

“…Next to different conspicuous bloom‐forming macroalgal genera like Sargassum , Gracilaria , or Ulva , there are a number of reports on blooming, somewhat cryptic taxa (Fricke et al., 2017; Littler et al., 2010; Lovelock et al., 2008; Vermeij et al., 2010). These so‐called mesoalgae, a term first introduced by Fricke et al.…”

“…These so‐called mesoalgae, a term first introduced by Fricke et al. (2017), bridge the classical size‐related terms macroalgae (visible by naked eye) and microalgae (visible under a microscope), and the term refers to all macroscopically visible algal elements (e.g., tufts, turfs, mats, and crusts), which can hardly be determined on a generic level without a microscope (Fricke et al., 2017; Juráň & Kaštovský, 2019). In this respect, mesoalgae can comprise different minute macroalgal stages (e.g., propagules, germlings, uniseriate, and fine filamentous thalli), as well as dense‐growing colonies of microalgae (e.g., cyanobacteria and diatoms).…”

Using Confocal Microscopy and Pigment Analyses to Detect Adverse Insecticide Effects in non-target Freshwater Diatom species - a proof-of-concept Using Nitzschia palea

“…Earlier studies made use of chlorophyll fluorescent-based assays to test the effects of pollutants on freshwater microalgae (Choi et al 2012 ) and phytoplankton (Seguin et al 2002 ). One such method includes the use of confocal laser scanning microscopy (CLSM) (Fricke et al 2017 ). This method has the advantage of visually and quantitatively determining the in-situ fluorescent properties of single celled organisms.…”