The biological environment of cobaltrich ferromanganese crust deposits

The biological environment of cobalt-rich ferromanganese crust deposits, the potential impact of exploration and mining in this environment, and data required to establish environmental baselines Tony Koslow CSIRO Marine Research Perth, Australia

The crust environment • Hard substrates – Seamounts & ridges – Enhanced currents • • • Winnow away sediments • Association with abrupt seafloor topography 800 - 2200 m depth for thickest crusts – Association with O 2 minimum (Hein 2002) Equatorial Pacific – Mid-Pacific Mts, Micronesia, Marshall Islands, Kiribati, Hawaii and Johnston Island

Topography enhances circulation

Unique deep-sea communities

High biomass, highly aggregated commercial fishery potential

Global seamount fisheries • • • >80 species fished from seamounts (Rogers 1994) Tropics/sub-tropics: alfonsino (Beryx spp), deepwater snapper N Pacific: pelagic armourhead, Sebastes spp Temperate S Pacific: orange roughy, oreos Sub-Antarctic: Patagonian toothfish • Evolutionary convergence (deep-bodied, strong burst swimmers) but from different families & orders – Flat seafloor slope & abyssal fishes: genera cosmopolitan (eg Coryphaenoides)

The unique hard-substrate seamount fauna

Soft-sediment v hard-substrate • Deposit feeders dominant – Burrowing worms • Suspension feeders dominant: – – – Hard & soft corals Sponges Hydroids, anemones Crinoids Brisingid starfish

Dominance by corals

Seamounts poorly sampled historically • • • Widespread distribution of seamounts only apparent after World War II from acoustic sounding records Rugged hard seamount environment difficult to sample with standard biological trawls Wilson & Kaufmann (1987): 597 species reported – 72% from only 5 seamounts – 27 species from entire SW Pacific – Endemism modest (~15%)

Recent discovery of seamount & deepwater coral diversity • • • Richer de Forges et al (2000): – 850 macro- & megabenthic species from 24 seamounts in Tasman/Coral Seas – 29 -34% new to science/potential endemics – Vertical zonation: no living reef-forming coral > 1400 m depth Parin et al (1997): 51% invertebrate endemism in E Pacific seamounts (Nazca & Sala y Gomez ridges) Cairns (1999): More species of cold-water than warmwater corals

No asymptote in discovery of seamount diversity (from Richer de Forges, Koslow & Poore (2000) Nature)

Exceptional deep-sea endemism Distribution localized to ridge system 21% mean coeff of community on seamounts within ridge, only 4% between ridges (same latitude, 1000 km separation) No species in common between S Tasmania & N Tasman/SW Coral Sea seamounts (60% of soft sediment decapod crustaceans of SE Australian slope have Indo-Pacific affinities)

The Galapagos of the deep • High endemism from high degree of reproductive isolation leading to local evolution/speciation – Topographic rectification of currents isolates seamounts & ridges – Evolution of reproductive strategies to limit loss outside seamount/ridge system • Limited larval duration or none at all (Parker & Tunnicliffe 1994)

Conservation implications • • Threat of extinction to localised heavily impacted species from widespread disturbance, eg fishing, mining Reduction from ~50% coral cover -> 95% bare rock on heavily trawled seamount off S Tasmania

Seamount communities in the Equatorial Pacific • • Limited data from Cross Seamount (18° N) S of Hawaii (Grigg et al 1987, Grigg 2002) Sparse (but potential for precious coral harvest), low diversity due to – weaker currents? – reduced surface productivity? – reduced O 2 or negative interactions of biota with crusts? – relative isolation? – vertical zonation Possible reduced impact from mining How representative is Cross?

Current state of knowledge • • > 46 cruises since 1981 to study Co-rich crusts No comprehensive benthic faunal surveys (!? ) • There is an urgent need for such research! • Interim precautionary view: – a substantial proportion of the benthic fauna on seamounts with cobalt-rich crusts will prove to be endemic to the local ridge system

Potential impacts of crust mining • • Loss of epifauna on mined crusts Enhanced sedimentation/release of metal species – Impacts on benthic fauna on adjacent parts of the seamount – Impacts on water column processes, eg primary productivity, grazers

Key issues • • What is the risk of extinction to endemic seamount species? What is the time scale for recovery, both for mined portions of the seamounts and adjacent areas affected by sedimentation?

Assessment issues (1) • • The diversity and biogeography (distributional range) of the seamount fauna in potential mining region How many seamounts will be mined, and what proportion (depth range) of each seamount? • Additional local seamounts that will not be mined? • How similar are the faunas of disturbed and undisturbed seamounts? • Relationship between the faunas of disturbed and undisturbed portions of these seamounts: vertical and topographic zonation generally observed

Assessment issues (2) • • • Additional activities (eg fishing and coral harvesting) that may also impact the region’s seamount fauna – May add to or mitigate mining impacts Impacts of enhanced sedimentation/release of metals on benthic fauna adjacent to mining area Will local seamounts be set aside in a reserve? What proportion should be conserved to reduce the risk of extinction to ‘acceptable’ levels and how is this to be determined?

Potential water column impacts + • • Sedimentation: – decreased light for primary production – Interference with grazing Metals: – Poison primary producers &/or grazers – Enhanced micronutrients (eg Fe) for primary production

Time scale for recovery • Not known but expected to be long: – Slow growth – Recruitment from adjacent seamounts uncertain and likely restricted (evolved to limit dispersal) – Decades? Centuries? Millennia? – probably depends on extent of impact, isolation, etc

Data requirements for environmental baselines • • The fauna of potentially mined and adjacent sites Endemism/distributional range of the fauna The impacts of mining on adjacent fauna Water-column impacts of mining

Seamount community assessment • • • Assess abundance, diversity, species composition Sampling stratified based on depth, topography (summit, rim, slope, base of seamount), current Standardise sampling tools & taxonomy – Photographic transects – Dredge with fine mesh cod-end to sample macro- & megafauna – Team of taxonomic specialists for community coverage

Assess & minimise extinction risk • • • Survey potential mining & protected sites with comparable fauna Assess levels of endemism & distributional range of fauna: – Survey seamount ridge systems or clusters – Assess biogeographic relations to regional fauna Assess genetic exchange within & between ridge systems

Assess impacts to adjacent, unmined portions of seamount • • Monitor water quality (sediment load, chemistry) under test mining conditions Controlled experiments (field & laboratory) to assess mining impacts on fauna of unmined portions of seamount

Water column impacts • • Assess water quality: sediment load, water chemistry Controlled field & lab experiments to assess potential impacts on – phytoplankton productivity – phytoplankton species composition – zooplankton grazing

Management framework • • Overall framework required to manage impacts of mining, fishing & coral harvesting Network of protected areas required based on – potential impacts – faunal diversity, endemism, & distribution