Draft:San Remo Marine Community
Threatened marine ecological community in San Remo, Victoria, Australia
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The San Remo Marine Community is a threatened intertidal and subtidal reef community located at the south-eastern corner of Western Port, Victoria, Australia, immediately north of the San Remo Bridge. It occupies a mixed substrate of mud, old (weathered) basaltic rock and sand, and is distinguished by an unusually rich assemblage of marine invertebrates—particularly opisthobranch molluscs (sea slugs) and bryozoans, many of which are considered rare. The community was listed as Threatened in Victoria in 1991 under the Flora and Fauna Guarantee Act 1988 (FFG Act), the first Victorian marine community to be so listed, and remains known from only a single locality in the state.[1][2][3]
| Type | Intertidal and subtidal reef and seagrass-flat community |
|---|---|
| Location | South-eastern Western Port, north of San Remo Bridge, Victoria, Australia |
| Substrate | Mud, old basaltic rock (soft weathered basalt), boulders and sand |
| Notable groups | Opisthobranch molluscs, bryozoans, crabs, echinoderms, sponges, seagrasses, algae, fish |
| FFG nomination ID | 14 |
| Conservation status | Threatened in Victoria (FFG Act 1988), listed 1991 |
| Principal historic threat | Proposed marina development (San Remo Quays) |
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Description
The San Remo Marine Community is an extensive intertidal and subtidal reef and seagrass flat. It is characterised by a combination of physical attributes not found elsewhere in Victoria, including a sheltered northerly aspect—uncommon along the Victorian coastline—adjacent to a fast-flowing deep channel, together with low wave energy over a mixed substrate of soft basalt, boulders and sand. Currents in the adjacent channel become very rapid during rising and falling tides.[1][2][3]
The community consists of an extremely species-rich assemblage of marine biota. It is best known for an unusually large number of opisthobranch mollusc and bryozoan species, but also includes intertidal algae, seagrasses, fish, sponges and a variety of crustaceans and echinoderms. Reefs elsewhere near the site are described as supporting relatively impoverished communities by comparison, and the diverse substrata are considered a key determinant of the community's richness, providing habitat suitable for a wide range of species.[1][2][3]
Of particular note is the relative abundance at the site of the rare bivalve, the Mud Ark (Anadara trapezia), a species once widespread and frequently found in fossil beds and Aboriginal middens, but which has declined markedly in range since European settlement.[2]
Distribution and setting
The community lies between the township of San Remo and the edge of the eastern tidal channel that connects Western Port with Bass Strait and runs in a south-west to north-east direction between Phillip Island and the mainland. It extends from the coastline out to the edge of the deep, fast-flowing channel, with the richest part of the community lying along the channel edge.[1][3]
Early documentation described the occupied area as roughly 600 × 300 metres near the township of San Remo.[3] A survey-based account placed the San Remo site on the coast about 1.75 km north-east of the bridge, extending seawards some 300–500 m to the deep channel between San Remo and Phillip Island.[4] The reef flats support a complex mosaic of substrata—sand, mud, coarse shingle, seagrass, algae and rock—with the exposed rocky areas more extensive at the western end near the No. 7 beacon. The dominant seagrasses recorded are Heterozostera tasmanica and Zostera muelleri, whose beds form part of large seagrass expanses in Western Port.[4] Within the Victorian marine bioregionalisation, the site falls within the Victorian Embayments (Western Port).[5]
At the time of listing, and for much of its documented history, the community was known from only this one locality in Victoria, although it was considered possible that similar communities might occur elsewhere in areas of comparable substrata.[1][3]
Biodiversity
Surveys have found the diversity of substrata at the site to be matched by a correspondingly rich invertebrate fauna. Over 630 species have been recorded from the site, of which 282 are conspicuous marine invertebrates; this is regarded as an underestimate because several animal groups, including sponges, cnidarians, worms and small crustaceans, had not been fully identified.[4]
Opisthobranchs (sea slugs)
The most distinctive components of the fauna are the opisthobranch molluscs and the crabs and bryozoans. The site is noted for supporting 93 species of opisthobranchs, a figure regarded by the Scientific Advisory Committee as rich for an intertidal habitat.[1][2] Repeated collecting by several observers over many years at the San Remo channel banks produced a list exceeding 120 opisthobranch species, including species then new to science or previously unrecorded for Victoria.[6] The naturalist Robert Burn, an authority on Opisthobranchia, collected at the site on numerous occasions from the early 1980s, and later published an annotated list of San Remo opisthobranchs.[3][6]
Two opisthobranch taxa associated with the community—the sea slug Platydoris galbana and the genus Rhodope—were themselves listed as threatened taxa under the FFG Act, and further undescribed taxa from the site were expected to be listed once formally described.[3][6] The 2025 action statement lists the marine opisthobranch Rhodope rousei and the sea slug Platydoris galbana among associated FFG-listed taxa.[2]
Other invertebrates
Other well-represented groups include bryozoans (colonial "lace corals"), crabs and echinoderms. Sixty-eight species of bryozoans and 40 species of crabs have been recorded from the reef flats and channel banks.[4] The unusually soft basalt substrate is also home to uncommon boring species, and the fauna includes a range of rare and uncommon animals such as the bivalves Barnea obturamentum and the Mud Ark (Anadara trapezia), the hermit crab Cancellus typus, the chiton Acanthochitona wilsoni, and the encrusting bryozoan Alcyonidium sp., among others.[4][2]
Conservation status and listing
Nomination and listing
The community was nominated for listing under the Flora and Fauna Guarantee Act 1988 on 27 April 1989 (nomination no. 14). The Scientific Advisory Committee (SAC) made a preliminary recommendation on 22 January 1991 and a final recommendation on 22 May 1991 that the community be supported for listing. The recommendation was endorsed by the SAC convenor, Neil Murray, on 19 June 1991.[1]
The SAC concluded that the community satisfied the primary criterion 2.2—that a community is significantly prone to future threats which are likely to result in extinction—on the basis of processes associated with a proposed marina at the site, the only known occurrence of the community. It also found that the sub-criterion 2.2.1 was satisfied, namely that the community is very rare in terms of the total area it covers, has a very restricted distribution, and has been recorded from only a few (in this case, one) localities. The SAC considered the community to be a unique assemblage of flora and fauna, and supported the nomination's claim that it is rich in bryozoans.[1]
The community was subsequently listed as Threatened in Victoria in 1991 and placed on Schedule 2 of the FFG Act.[2][3] It is significant as the first marine community listed under the Act.[4]
Action statements
An action statement for the San Remo Marine Community was first published in 1992 (Flora and Fauna Guarantee Action Statement No. 18) and reissued for web publication in 2003, retaining the original text. This document set out management objectives including maintaining the community's integrity at San Remo, identifying its spatial extent, and mapping its distribution within Victoria.[3]
In November 2025 a combined action statement was published by the Department of Energy, Environment and Climate Action (DEECA) covering both the San Remo Marine Community and the related Western Port Bryozoan Reef Community, treating the two as ecologically similar communities subject to common threats and conservation actions.[2]
Legislative protection
Listing under the FFG Act triggers protection of the community's flora and provides for the determination of Critical Habitat and, as a last resort, the issuing of an Interim Conservation Order. A range of other legislation also applied to the site, including the Fisheries Act 1968 (later the Fisheries Act), the Wildlife Act 1975 (permits to take listed invertebrates such as Rhodope spp. and Platydoris galbana), the Marine Act 1988, and the Planning and Environment Act 1987.[3][2]
Threats
The threat that prompted the community's listing was a proposal to develop a marina at the site. Bass Shire Council proposed the San Remo Quays marina, and permission to develop on the originally selected site—the only known site of the community—was refused under the Planning and Environment Act 1987. The associated processes of concern included excavation and construction, dredging, sediment deposition, changes to water flow and current patterns, and changes to water quality (for example from slip yards, car-park runoff and anti-fouling paints). Because knowledge of the site's hydrology was incomplete, protective measures were recommended to be conservative.[1][3][4]
The 2025 action statement identifies a broader and updated set of threats to the community, grouped into several categories:[2]
- Climate change — rising water temperatures, marine heatwaves, and ocean acidification.
- Habitat loss, degradation or modification — loss of key habitat features, harmful algal blooms, and changes in wave energy.
- Human disturbance — anchoring and mooring, construction and infrastructure, dredging, recreational activities and fishing, trampling by humans, and a general lack of awareness of the community's conservation needs.
- Introduced species — introduced plants, algae and habitat-forming invertebrates.
- Pathogens and disease — introduced marine microbial pathogens.
- Pollutants and toxicants — litter, oil spills, and pollution from both marine and terrestrial sources.
Research history
The San Remo fauna has been surveyed extensively by the Marine Research Group of Victoria (later part of the Field Naturalists Club of Victoria) since 1981, with the site visited many times over subsequent decades; one member, David Howlett, is recorded as having visited more than 170 times and as having discovered numerous still-unnamed species there.[4][6] The fauna was also sampled in 1987 by the Marine Research Group and by Kinhill Engineers as part of the environmental effects statement prepared for the proposed marina.[1][3] The prominence of the site in Victorian opisthobranch research is reflected in Robert Burn's 2006 checklist and bibliography of the Opisthobranchia of Victoria and the Bass Strait area, which repeatedly cites San Remo (Western Port) as a source of new and unrecorded sea-slug records.[6]
Related community
The Western Port Bryozoan Reef Community, a species-rich subtidal biogenic reef in Western Port covering approximately 1.74 km², was listed as Threatened in Victoria in 2022 and is addressed together with the San Remo Marine Community in the 2025 action statement. Its reef substrate is built by three bryozoan species—Triphyllozoon munitum, T. moniliferum and Celleporaria foliata—that form large colonies of up to 1.5 m vertical relief, locally known as "The Corals".[2]
Marine protection context
The San Remo Marine Community lies within Western Port, a region identified in reviews of Victoria's marine protected area (MPA) network. Such reviews have noted that Victoria has among the smallest areas of marine protected and no-take waters of any Australian jurisdiction, and have highlighted the ecological richness and conservation importance of Western Port's habitats, including seagrass beds and biogenic reefs.[5]