Fabricius KE et al. (2014), Ecological effects of ocean acidification and h...

ECB-ART-50080

Proc Biol Sci 2014 Jan 22;2811775:20132479. doi: 10.1098/rspb.2013.2479.

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Ecological effects of ocean acidification and habitat complexity on reef-associated macroinvertebrate communities.

Fabricius KE , De'ath G , Noonan S , Uthicke S .

Abstract
The ecological effects of ocean acidification (OA) from rising atmospheric carbon dioxide (CO2) on benthic marine communities are largely unknown. We investigated in situ the consequences of long-term exposure to high CO2 on coral-reef-associated macroinvertebrate communities around three shallow volcanic CO2 seeps in Papua New Guinea. The densities of many groups and the number of taxa (classes and phyla) of macroinvertebrates were significantly reduced at elevated CO2 (425-1100 µatm) compared with control sites. However, sensitivities of some groups, including decapod crustaceans, ascidians and several echinoderms, contrasted with predictions of their physiological CO2 tolerances derived from laboratory experiments. High CO2 reduced the availability of structurally complex corals that are essential refugia for many reef-associated macroinvertebrates. This loss of habitat complexity was also associated with losses in many macroinvertebrate groups, especially predation-prone mobile taxa, including crustaceans and crinoids. The transition from living to dead coral as substratum and habitat further altered macroinvertebrate communities, with far more taxa losing than gaining in numbers. Our study shows that indirect ecological effects of OA (reduced habitat complexity) will complement its direct physiological effects and together with the loss of coral cover through climate change will severely affect macroinvertebrate communities in coral reefs.

PubMed ID: 24307670
PMC ID: PMC3866403
Article link: Proc Biol Sci

Article Images: [+] show captions

	Figure 1. Indo-Pacific reef communities with contrasting structural complexity. (a) Structurally complex reef (complexity rating value 4–5) with branching, tabulate and foliose coral morphologies. (b) Structurally simplified communities dominated by massive coral morphologies (complexity 2–3), as found in areas of chronic disturbance as shown here from one of the PNG CO2 seeps. (c) Flattened reef lacking three-dimensional structure (complexity 0–1), as found after major disturbance. (Online version in colour.)
	Figure 2. Ratios of the densities or number of taxonomic units of macroinvertebrates at high-CO2 relative to control sites (n = 35 surveys). Circles mark the estimated ratios, error bars show lower and upper 95% CIs (see electronic supplementary material, tables S5 and S6). Differences are significant (p < 0.05) if the error bars do not include the value 1.0.
	Figure 3. Partial effects plots showing the relationships of macroinvertebrates to CO2, complexity and substratum type (HC: quadrats dominated by living hard corals; DS: substrata devoid of macrofauna). Circles indicate estimated marginal mean densities or number of taxonomic classes per 0.25 m−2 (total counts = all organisms combined; mobile/sessile and calcifying/non-calcifying = densities of all mobile/sessile and calcifying/non-calcifying organisms combined). Error bars are lower and upper 95% CIs. Estimated percentage change (high CO2 to control, complexity rating = 0 to complexity rating = 5, and DS to HC) and their 95% CIs are shown in the panels.
	Figure 4. Conceptual diagram of the loss of coral cover owing to climate-change-related disturbances and the indirect and direct effects of OA on reef-associated macroinvertebrates.

References [+] :

Alvarez-Filip, Flattening of Caribbean coral reefs: region-wide declines in architectural complexity. 2009, Pubmed, Echinobase