Know Thy Anemone: A Review of Threats to Octocorals and Anemones and Opportunities for Their Restoration

Abstract

In studies of habitat-forming species, those that are not spatially dominant are often considered "non-primary" habitat and may be overlooked. This is despite the fact that minority habitat formers can provide critical complexity, food, and other services that underpin ecosystem biodiversity. Octocorals and anemones are found in marine and estuarine habitats across all climate zones. Despite their potentially important ecological roles, to date there have been few studies of their specific threats and stressors or attempts at their restoration. Here we review studies of the ecology of octocorals and anemones with a focus on threats and restoration. We identify many threats including habitat damage, collection and trade, disease, predation, pollution, and the most widespread-climate change. While evidence suggests that some octocorals and anemone populations may be more resilient to disturbances than stony corals because they often recruit and grow quickly, resilience is not guaranteed. Instead, resilience or susceptibility within this large group is likely to be site and species specific. We find that the loss of octocorals and anemones has been difficult to quantify as most species have no hard structures that remain following a mortality event. Only through long-term monitoring efforts have researchers been able to document change in these populations. Due to the increasing extent and severity of human impacts in marine ecosystems, restoration of habitat forming species is becoming increasingly necessary after disturbance events. To illustrate the challenges ahead for octocoral and anemone restoration, we present two examples of ongoing restoration efforts assessed against the International Standards for the Practice of Ecological Restoration. Restoration planning and implementation progress are documented for the Mediterranean red coral Corallium rubrum and the temperate Australian cauliflower soft coral, Dendronephthya australis. This review and the detailed case studies demonstrate that while some octocorals and anemones can provide resilient habitat within reef systems, a greater research focus on their ecology, threats, and restoration potential is urgently required.

What eats a cauliflower coral? An assessment of predation on the endangered temperate soft coral,

“…Seagrasses are widely agreed to be key nursery habitats for many estuarine species (Bloomfield and Gillanders 2005;Bertelli and Unsworth 2014;Unsworth et al 2019). In contrast, soft coral habitats are generally considered an inferior habitat relative to scleratinian corals (Epstein and Kingsford 2019;Steinberg et al 2020). Our results corroborated those of Corry et al (2018) and Poulos et al (2013), which highlights the value of soft coral habitats for fish assemblages, including for species of commercial and recreational value.…”

“…Soft corals are often ignored in ecological studies, including in food web analyses (Steinberg et al 2020). In part, this may be due to the evidence that in some systems, abundant soft coral habitats are indicators of habitat loss (Norstro ¨m et al 2009) and that they often contain natural toxins that deter predation (Coll et al 1982;Fernando et al 2017).…”

Spawning, embryogenesis, settlement, and post‐settlement development of the gorgonian Plexaura homomalla

“…Espitia, 2013; Linares et al, 2008; Montseny et al, 2019; Oren & Benayahu, 1997). However, propagation based on settling larvae will be necessary for species such as alcyonaceans, which lack axes and cannot be propagated using colony fragments (Steinberg et al, 2020). Bramanti et al (2007) examined field settlement to tiles, which could be transported to new areas, but ex situ development of larvae may be important in repopulating areas where natural settlement is too low to reestablish populations (Vanderklift et al, 2020).…”

Heteractis magnifica Sea Anemone Population Dynamics at Village Reef, Perhentian Kecil, Malaysia: Monitoring of Growth, Formations, and Hosting Status

“…The sea anemones’ ( Actiniaria) ability to reproduce asexually, and their lack of skeletal structure allows rapid formation and community expansion in suitable environments (Steinberg et al . 2020).…”

“…The sea anemones' (Actiniaria) ability to reproduce asexually, and their lack of skeletal structure allows rapid formation and community expansion in suitable environments (Steinberg et al 2020). Sea anemones can continually produce viable nodules for colonisation of neighbouring patches, where, given favourable environmental factors, sexual reproduction is actively suppressed in favour of rapid, asexual colonisation (Brace & Quicke 1986).…”