Forgotten underwater forests: The key role of fucoids on Australian temperate reefs

Abstract

Kelp forests dominated by species of Laminariales are globally recognized as key habitats on subtidal temperate rocky reefs. Forests characterized by fucalean seaweed, in contrast, receive relatively less attention despite being abundant, ubiquitous, and ecologically important. Here, we review information on subtidal fucalean taxa of Australia's Great Southern Reef, with a focus on the three most abundant and widely distributed genera (Phyllospora, Scytothalia, and Sargassum) to reveal the functionally unique role of fucoids in temperate reef ecology. Fucalean species span the entire temperate coastline of Australia (~71,000 km2) and play an important role in supporting subtidal temperate biodiversity and economic values on rocky reefs as well as in adjacent habitats. Climatic and anthropogenic stressors have precipitated significant range retractions and declines in many fucoids, with critical implications for associated assemblages. Such losses are persistent and unlikely to be reversed naturally due to the life history of these species and colonization of competitors and grazers following loss. Active restoration is proving successful in bringing back some fucoid species (Phyllospora comosa) lost from urban shores and will complement other passive and active forms of conservation. Fucalean forests play a unique role on subtidal temperate reefs globally, especially in Australia, but are comparatively understudied. Addressing this knowledge gap will be critical for understanding, predicting, and mitigating extant and future loss of these underwater forests and the valuable ecosystem services they support.

Tropicalisation of temperate reefs: Implications for ecosystem functions and management actions

“…Observational and experimental studies show substantial declines in α diversity through loss of overall abundance and number of species when seaweed forests disappear (Graham, 2004;Ling, 2008). Loss of species caused by the replacement of kelp forests by other seaweeds may be offset if these provide similar microhabitats (Coleman & Wernberg, 2017), though species identity is likely to change. For example, co-occurring cool-water laminarian kelps and more warm-tolerant Sargassum species support significantly different associated communities (Coleman & Wernberg, 2017) and a shift from kelp to Sargassum (Tanaka et al, 2012;Wernberg et al, 2016) will likely reflect these changes.…”

“…Loss of species caused by the replacement of kelp forests by other seaweeds may be offset if these provide similar microhabitats (Coleman & Wernberg, 2017), though species identity is likely to change. For example, co-occurring cool-water laminarian kelps and more warm-tolerant Sargassum species support significantly different associated communities (Coleman & Wernberg, 2017) and a shift from kelp to Sargassum (Tanaka et al, 2012;Wernberg et al, 2016) will likely reflect these changes. In contrast, where seaweed forests are replaced by tightly packed low-lying turf species (Figure 1c) biodiversity is likely to decline (Vergés, Tomas, et al, 2014).…”

Distribution models predict large contractions of habitat‐forming seaweeds in response to ocean warming

“…Such substantial changes in canopy cover would have severe implications for the whole coastal ecosystem, as these species are habitat‐formers which provide three‐dimensional structure, food and environmental conditions supporting a broad array of associated organisms (Coleman, Vytopil, Goodsell, Gillanders, & Connell, ; Connell, ; Ling, ; Tuya, Wernberg, & Thomsen, ; Wernberg & Goldberg, ). These temperate canopy‐forming seaweeds are therefore bioindicators of the integrity of Australian reef ecosystems which support a multitude of recreational, commercial and scientific interests (Bennett et al., ; Coleman & Wernberg, ; Poloczanska et al., ; Wernberg, Krumhansl, Filbee‐Dexter, & Pedersen, ).…”

Harnessing synthetic biology for kelp forest conservation1

“…, Krumhansl et al. , Coleman and Wernberg ), threatening valuable ecosystem goods and services derived from the sea (Costanza et al. , Bennett et al.…”