Sargassum amaliae (an alga)

Unsuccessful threatened species list nomination
4 May 2013

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1. Reason for Conservation Assessment by the Committee

This advice follows assessment of information gathered through the Commonwealth's partnership with Queensland on:

  • Sargassum amaliae (an alga)

2. Summary of Species Details

Taxonomy

Conventionally accepted as Sargassum amaliae Grunow 1874.

There is some uncertainty about the taxonomy of the genus Sargassum in tropical Australia (Phillips and Price, 1997; Millar, pers. comm., 2012; McCook, pers. comm., 2012). Sargassum amaliae can be confused with other Sargassum species which are widespread, therefore it can be difficult to identify in field surveys.

For the purpose of this assessment the Committee recognises Sargassum amaliae as a distinct species.

State/ Territory Listing Status

This species is not listed as threatened under Queensland legislation.

Description

Sargassum amaliae is a brown alga with several primary branches up to 45 cm in length arising from the base. Primary branches produce densely crowded stems composed of many simple leaf-like structures 20–40 mm long and 3–5 mm broad. These structures have rounded or tapering tips and numerous spherical sacs 2–3 mm in diameter (Phillips, pers. comm., 2010). Morphology of Sargassum species can be influenced by environmental conditions, and hence identification depends on DNA sequence data (Millar, pers. comm., 2012).

Distribution

In Australia, Sargassum amaliae is known from Queensland (Bostock and Holland, 2010) and Norfolk Island (Lewis, 1985; Millar, 1999; Guiry and Guiry, 2012). It occurs in the lower intertidal zone on wave-exposed rocky substrata (Phillips, pers. comm., 2010) and possibly also in subtidal habitat (Diaz-Pulido, pers. comm., 2011).In Queensland the species has been recorded from:

  • Bribie Island (isotype) – specimen collected in the 1860s and held by the National Herbarium of Victoria (Phillips and Blackshaw, 2011);
  • Rockingham Bay near Cardwell – specimen collected in 1870 and held by the National Herbarium of Victoria (Phillips and Blackshaw, 2011);
  • Cooktown – doubtful record (Phillips and Blackshaw, 2011);
  • Caloundra – specimens collected in 1961 and held by the Queensland Herbarium (Phillips and Blackshaw, 2011); and
  • Point Cartwright at Mooloolaba – description only (Cribb, 1958).

Quantitative surveys in 2004–06 showed that S. amaliae no longer occurred at Caloundra and Point Cartwright (Phillips and Blackshaw, 2011; Phillips, pers. comm., 2010) where photographs, descriptions and herbarium specimens documented well-developed populations in the mid 1950s and 1961 (Cribb, 1958; Phillips, pers. comm., 2010). The Bribie Island specimen was likely to have drifted from Caloundra, and the Cooktown record is regarded as spurious (Phillips and Blackshaw, 2011). The species has not been recorded in the well-studied Townsville region, where eight common Sargassum species occur (Martin-Smith, 1993).

The most recent record of this species in Queensland is from Caloundra in 1961. Recent surveys suggest that it no longer occurs at this or at any of the other previously known Queensland sites (Phillips and Blackshaw, 2011).

A large source of uncertainty in this assessment is the current distribution of S. amaliae because other Sargassum species with which it might be confused on morphological grounds are widely distributed.

Relevant Biology/Ecology

Sargassum species generally reach sexual maturity at six months, are estimated to have a life expectancy of 5–15 years (Womersley, 1987) and persist for several decades as stable populations (Phillips, pers. comm., 2010).

Sargassum amaliae is a ‘foundation’ species (Cribb, 1958) that provides three-dimensional habitat, food and protection for many invertebrates (including crustaceans, mites, echinoderms and polychaetes) and algae. Sargassum species are also an important food source for Chelonia mydas (green turtle) (Garnett et al., 1985), which is listed as vulnerable under the EPBC Act.

Threats

Known

The only known threats to S. amaliae are the impacts associated with urbanisation, such as eutrophication (nutrient enrichment by sewage) which affects recruitment due to the sensitivity of juveniles to high nutrient levels (Phillips, pers. comm., 2010). Range contractions of Sargassum species and other large brown algae have occurred world-wide, including Mediterranean-wide extinctions (e.g. Thibaut et al., 2005; Pinedo et al., 2007). Large brown algal communities typically disappear from urbanised coastlines and areas in the vicinity of sewage outfalls (Brown et al., 1990; Pinedo et al., 2007).

Potential

There are no known potential threats to this species.

3. Public Consultation

Notice of the proposed amendment was made available for public comment for 30 business days. No comments were received from members of the public. Comments received from six algal experts as a result of targeted consultation have been considered as part of this assessment.

4. How judged by the Committee in relation to the EPBC Act criteria and Regulations

Criterion 1: It has undergone, is suspected to have undergone or is likely to undergo in the immediate future a very severe, severe or substantial reduction in numbers.

For this criterion to be met, the population size of this species must have been observed, estimated, inferred or suspected to have declined by at least 30% over the last ten years or three generations of the species (whichever is the longer), with this threshold value (30%) linked specifically in the Act to threats that may not have ceased or may not be reversible.

Not eligible

Criterion element Evidence
Reduction in numbers Insufficient data – Based on the disappearance of S. amaliae from Caloundra and Point Cartwright, this speciesis inferred to have declined. However, as the species is difficult to recognise in the field, there are insufficient data to determine the severity of this decline and whether it occurred over a timeframe appropriate to this criterion, therefore the species is not eligible for listing under this criterion.

Criterion 2: Its geographic distribution is precarious for the survival of the species and is very restricted, restricted or limited.

For this criterion to be met, this species' extent of occurrence must be less than 20 000 km2 and/or its area of occupancy must be less than 2000 km2, its geographic distribution must be precarious for its survival based on severe fragmentation or known to exist at a limited location, and a continuing decline must be observed, inferred or projected based on the degree of threat operating on the species.

Not eligible

Criterion element Evidence
Geographic distribution Insufficient data – The Committee considers that the species’ range cannot be accurately determined due to the lack of surveys undertaken in potential sub-tidal habitat and the difficulty in identifying the species in the field.
AND
Geographic distribution precarious Insufficient data – The species is difficult to recognise in the field and as such its distribution is uncertain. Therefore, the species is not eligible for listing under this criterion.

Criterion 3: The estimated total number of mature individuals is very low, low or limited; and either

  1. evidence suggests that the number will continue to decline at a very high, high or substantial rate; or
  2. the number is likely to continue to decline and its geographic distribution is precarious for its survival

For this criterion to be met, the estimated number of mature individuals of this species must be less than 10 000, and the rate of continuing decline is at least 10% in 10 years or three generations, or there is a continued decline and the geographic distribution is precarious, having regard to the degree of threat operating on the species.

Not eligible

Criterion element Evidence
Total no. of mature individuals Insufficent data – refer to Section 5 below.
AND
Rate of continued decline Insufficient data – refer to Section 5 below.
OR

Total no. of mature individuals

Insufficient data – refer to Section 5 below.
AND

Continued decline likely

Insufficient data – Eutrophication (nutrient enrichment) from the continuing development of the Queensland coast would be expected to reduce the geographic distribution and number of populations of S. amaliae (Phillips, pers. comm., 2010), particularly given the species' already fragmented distribution and limited dispersal capabilities. However, the species’ distribution is uncertain and there is no evidence to suggest this threat is affecting the Norfolk Island population.
AND
Geographic distribution precarious Insufficient data – See Criterion 2

Criterion 4: The estimated total number of mature individuals is extremely low, very low or low

For this criterion to be met, the estimated total number of mature individuals must be less than 1000.

Not eligible

Criterion element Evidence
Total no. of mature individuals Insufficent data – refer to Recommendation 5 below.

Criterion 5: Probability of extinction in the wild that is at least

  1. 50% in the immediate future; or
  2. 20% in the near future; or
  3. 10% in the medium-term future

For this criterion to be met, the probability of extinction in the wild must be at least 10% in the medium-term future (within 100 years).

Not eligible

Criterion element Evidence
Probability of extinction in the wild There has been no formal modelling of the probability of extinction of this species.

5. Recommendations

The Committee recommends that Sargassum amaliae is not eligible for inclusion in the list referred to in section 178 of the EPBC Act. There are insufficient data to assess the species’ status effectively and thus the Threatened Species Scientific Committee finds this species to be ‘data deficient’.

The species is difficult to recognise in the field and as such its distribution is uncertain. Given that the species could occur in other areas, it is unlikely that the whole of the species’ population would be impacted by stochastic events or a single threatening process. Until further surveys and associated molecular work are undertaken the Committee cannot conclude that the species’ geographic distribution is precarious for the survival of the species or limited. The Committee therefore considers that the species is not eligible for listing against any of the criteria.

The Committee recommends the following research could be undertaken to overcome the lack of data:

  • Survey appropriate habitats within the known previous extent of occurrence of the species, particularly in the northern end of the Queensland part of the species' range (especially Rockingham Bay) and Norfolk Island. Surveys should include rocky substrates in both intertidal and subtidal zones.
  • Ensure that identification of the species from the above surveys is verified using appropriate molecular techniques.

Until such research is done, the Committee is unable to undertake any form of risk analysis for this species.

The Threatened Species Scientific Committee encourages a subsequent nomination of this species for status assessment should the data deficiency be adequately addressed.

Threatened Species Scientific Committee
4 May 2013

6. References cited in the advice

Bostock PD and Holland AE (2010). Census of the Queensland Flora. Queensland Herbarium Biodiversity and Ecosystem Sciences, Department of Environment and Resource Management, Brisbane.

Brown VB, Davies SA and Synnot RN (1990). Long-term monitoring of the effects of treated sewage effluent on the intertidal macroalgal community near Cape Schanck, Victoria, Australia. Botanica Marina 33: 85–98.

Cribb AB (1958). An ecological and taxonomic account of the marine algae of south-eastern Queensland. PhD thesis, University of Queensland, Brisbane, Australia.

Diaz-Pulido, G (2011). Personal communication by email. 7 December 2011. Lecturer, Griffith University, Queensland.

Department of Sustainability, Environment, Water, Population and Communities (DSEWPaC) (2012). Environmental Resources Information Network (ERIN) database. Accessed 5 March 2012.

Garnett ST, Price IR and Scott FJ (1985). The diet of the green turtle Chelonia mydas (L.) in Torres Strait. Australian Wildlife Research 13: 103–112.

Guiry MD and Guiry GM 2012. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.
Viewed: 10 May 2012
Available on the Internet at: http://www.algaebase

Lewis JA (1985). Checklist and bibliography of benthic marine macroalgae recorded from northern Australia II. Phaeophyta. Defense Science and Technology Organisation. Department of Defense, Melbourne. Report MRL-R-962, pp. 1–40.

Martin-Smith KM (1993). The phenology of four species of Sargassum at Magnetic Island, Australia. Botanica Marina 36: 327–334.

McCook L (2012). Personal communication by phone, 22 March 2012. Great Barrier Reef Marine Park Authority.

Millar AJK (2012). Personal communication by email, 20 March 2012. Principal Research Scientist, Royal Botanic Gardens, Sydney.

Millar AJK (1999). Marine benthic algae of Norfolk Island, South Pacific. Australian Systematic Botany 12:479–547.

Phillips JA (2010). Personal communication by nomination form, 23 March 2010, EcoAlgae Research Pty Ltd.

Phillips JA and Blackshaw JK (2011). Extirpation of macroalgae (Sargassum spp.) on the subtropical east Australian coast. Conservation Biology 25(5): 913–921.

Phillips JA and Price IR (1997). A catalogue of Phaeophyta (brown algae) from Queensland, Australia. Australian Systematic Botany 10: 683–721.

Pinedo S, García M, Satta MP, deTorres M and Ballesteros E (2007). Rocky-shore communities as indicators of water quality: A case study in the northwestern Mediterranean. Marine Pollution Bulletin 55: 126–135.

Thibaut T, Pinedo S, Torras X and Ballesteros E (2005). Long-term decline in the populations of Fucales (Cystoseira spp. and Sargassum spp.) in the Albères coast (France, North-western Mediterranean). Marine Pollution Bulletin 50:1472–1489.

Womersley HBS (1987). The marine benthic flora of Southern Australia Part II. Adelaide, South Australian Government Printing Division.