Substratum selection in coral reef sponges and their interactions with other benthic organisms

Abstract

Substratum preferences and contact interactions among sessile organisms can be a major determinant of biotic gradients in the structure of benthic communities on coral reefs. Sponges are a substantial component of these communities, but their substratum requirements and interactions with other benthic taxa are poorly understood. Here, we quantified sponge substratum preferences and interactions from 838 randomly selected photo-quadrats across different depths (5, 10 and 15 m), exposure (sheltered and exposed), and substratum topography (horizontal, inclined and vertical surfaces) on coastal coral reefs in Kimbe Bay. A high proportion (55%) of sponge colonies were associated with dead coral, unconsolidated coral rubble (7%) and calcium carbonate rock (CaCO3 rock) (7%), even though they represented only 10%, 4% and 1% of the available substratum, respectively. Sponges interacted most frequently with algae (~ 34%), corals (~ 30%) and crustose coralline algae (CCA ~ 19%) that represented ~ 46%, ~ 18% and ~ 14% of the substratum cover, respectively. The microhabitat preferences of sponges and frequency of interactions with other taxa were mostly consistent across various exposure, depth and substratum topography conditions. Most interactions appeared to be “stand-offs” (71%) which are interactions with no clear winner or loser. However, when overgrowth occurred, sponges were usually winners, overgrowing corals (92%), CCA (81%) and macroalgae (65%). Three sponge species Dysidea sp1, Lamellodysidea cf. chlorea and Lamellodysidea chlorea accounted for 51% to 96% of the overgrowth of sponges over algae, corals and CCA, but there was no one species found to always win or lose. Our results suggest that sponges avoid other biological substrata by preferentially settling on dead coral, coral rubble and CaCO3 rock, but when they do come into contact with algae and corals, they frequently overgrow their spacial competitors.

Does the microbial community play a role in the different colour morphs of the breadcrumb sponge Halichondria panicea?

“…As noted previously (Fig. 2), both colour morphs were found on rocks covered in coralline algae, as sponges prefer to attach to non-living substrates and interact more frequently with crustose coralline algae, algae, corals, ascidians and zoanthids (González-Murcia et al 2023). Thus, coralline algae may have been introduced into sponge samples as a result of cross-contamination while collecting them from coralline algae-covered rock surfaces.…”

“…The coralline Phymatolithon has a non-geniculate habit and is highly abundant in UK coastal areas (Chamberlain 1990;Jeong et al 2021). Sponges interact most frequently with algae, corals and crustose coralline algae, where coralline algae represent approximately 14% of the substratum cover (González-Murcia et al 2023). As noted previously (Fig.…”

Cellular adaptations of the scleractinian coral Madracis pharensis to chronic oil pollution in a Mediterranean shipwreck

“…Competition for space between corals and sponges is a classic example of a biological factor affecting species' assemblages in natural and artificial substrates, in the Mediterranean and elsewhere (Chadwick and Morrow, 2011;Kayal and Adjeroud, 2022). Several life-traits allow sponges to thrive and outcompete other species in limiting environments such as those found in shipwrecks; for example, sciaphilic species and physical and chemical defenses against other benthic organisms (Wulff, 2006, Gonzaĺez-Murcia et al, 2023. We believe that less competition with sponges is probably the main reason behind the increase in Madracis' percentage of cover at both sampling sites in the 2022 survey.…”

Neglected biodiversity and ecological functioning – fish community structure associated with Antipatharia (black corals) on shallow reef ecosystems

“…Other habitat-forming benthic groups have been previously considered (e.g. octocorals and sponges - Moynihan et al 2022, González-Murcia et al 2023; however, antipatharians are commonly neglected from coral reef monitoring programs and studies. A greater effort to quantify the abundance and ecological roles of the different benthic groups would lead to a more holistic understanding of how the different benthic taxa interact to support coral reef biodiversity.…”