SUMMARY OF EVIDENCE OF MR J A (SANDY) BARTLE IMPORTANCE OF COPEPODS - PowerPoint PPT Presentation

SUMMARY OF EVIDENCE OF MR J A (SANDY) BARTLE

IMPORTANCE OF COPEPODS • Mesozooplankon (mostly copepods) are the largest group of consumers on the CR. • Copepods are filter-feeders, constantly sweeping the water for minute phytoplankton • They form the main link between phytoplankton and all other consumer groups. • Most abundant copepod species migrate down by day to well over 250m below surface • Some migrate as far as the seafloor

VULNERABILITY OF COPEPODS • New research on the effect of increased sediment on copepods was recently published (Arendt et al.2011) • The research was stimulated by the appearance of subsurface (100 m depth) sediment plumes generated by tidal re-suspension, following the retreat of the Greenland Ice Sheet • Sizes of sediment particles were similar to those expected to be generated on the Chatham Rise • Clay grains (2-3 μm ) had the highest concentration in upper waters due to the sinking of the larger particles

Calanus finmarchicus • very abundant in the North Atlantic • Calanus finmarchicus is the key food of both herring and cod

EFFECT OF SEDIMENT • New research showed  sediment particles replaced food in the gut of Calanus finmarchicus  reduced food uptake

SIGNIFICANCE FOR MARINE PRODUCTIVITY • NIWA research on CR copepods found the mean turnover time was 7.3 days (McClatchie et al. 2004). • Spring blooming of copepods depends on their ability to reproduce very rapidly once phytoplankton become abundant. • Greenland research showed egg production in Calanus finmarchicus declined from close to 23 eggs/day to near zero.

EGG PRODUCTION • Copepods were immersed in water of moderate-high sediment concentration (over 20mg/l) • Result: egg production of Calanus finmarchicus vastly reduced

VERTICAL MIGRATION • 15-50% of zooplankton biomass migrates down as far as 800m. • Euphausiids are by far the most abundant macrozooplankton on the Chatham Rise (Robertson et al. 1978). • Euphausiids are a key food for pelagic fish, squid and seabirds. • Euphausiids are filter-feeders like copepods and may not be able to distinguish mineral particles from food.

ZOOPLANKTON MIGRATION INTO THE SEDIMENT PLUME • Euphausiids commonly migrate down to the sea floor to feed on detritus • Migration occurs at rates of up to 100m/hr • The most abundant euphausiid on the CR is Nematoscelis megalops • These reach depths of 300-500 m by day (Mauchline & Fisher 1969) • Will descend into the sediment plume

CHATHAM RISE WATER IS NATURALLY CLEAR • Very clear water to the north of the Chatham Rise (Nodder 2013) • Background minimum particle concentration in the water column of 0.012 mg/l • This rose to a maximum of c.0.55mg/l, 150m above the sea floor of the crest of the CR • This is far below the density where copepod egg production declined (Arendt 2011)

1976 SURVEY • I participated in a survey of the Chatham Rise and Bounty Trough in October – November 1976 • Good coverage of the northern slope along 41˚20’S and the southern slopes near 44˚30’S plus the Chatham Is area • Never traversed the crest of the rise • The time of year of the survey was perfect  migrant seabirds from the North Pacific and South America had already returned  winter visitors to the CR from the Southern Ocean were still present in abundance

1976 SURVEY RESULTS • Thirty-two seabird species were recorded on this voyage • Reliable records of another 20 were obtained from published literature and tracking studies, most at other times of the year • Many species thought by Thompson and Taylor to occur on the Chatham Rise never recorded there • Several others, unmentioned by these experts in their evidence, do occur there, sometimes in abundance

1976 SURVEY CONCLUSIONS • Discrepancies in the three descriptions of the seabird fauna in evidence show the importance of systematic surveys of seabirds at sea • Systematic survey provide essential baseline data • In a global context, the 52 species recorded on the Chatham Rise compare very favourably with the much smaller number of oceanic species (only 17) which live and breed in the temperate North-east Atlantic

SALVINS ALBATROSS • by far the most numerous albatross on the CR • 41,000 breeding pairs on Bounty Is in 2010 • photo courtesy NIWA

• Obvious concentration of Salvins GPS locations of Salvin’s albatrosses from the Albatross foraging on the CR (and Bounty Is (green dots) and Snares Is (red dots) Hikurangi Eddy). throughout the year, • The CR is a vital feeding area for this including during their winter migration to the declining Nationally Critical Species Humboldt Current (data plot courtesy NIWA). (2013 DOC ranking).

BOUNTY ISLANDS Without the food resources of the Chatham Rise, the future of this declining Nationally Critical species (2013 DoC ranking) would be very bleak

ACTUAL THREATS TO SEABIRDS POSED BY MARINE MINING • Low-frequency sound attraction to diesel generators  This has been documented for four petrel species in two different families  Uncertain whether such generators will be installed and, if so, how efficiently they might be insulated • The extent of this risk depends on the generators installed and insulation adopted

LIGHT ATTRACTION • Attraction to vessel lights by nocturnal seabirds (most species other than albatrosses) • Seabird expert conferencing group suggested conditions • Effectiveness of green lighting is uncertain • Expert conferencing group recommended a trial to determine effectiveness • Conditions dependent on outcome of trial

POTENTIAL THREATS TO SEABIRDS POSED BY MARINE MINING • Ecosystem effects caused by ingestion of sediment by zooplankton • Seabird feeding on small zooplankton containing grit • Seabird attraction to galley waste and dredge discharges

ECOSYSTEM EFFECTS OF INGESTION OF SEDIMENT BY ZOOPLANKTON • Sediment ingestion may reduce breeding rate of key organisms • Almost no research on this topic • No research undertaken by CRP • This risk is uncertain

SEABIRDS FEEDING ON SMALL ZOOPLANKTON CONTAINING GRIT • Many Chatham Rise species feed directly on small zooplankton • May result in seabirds ingesting grit with possible mortal impacts, as with plastic pellets (many publications from the North Pacific) • No research has been proposed or undertaken on this topic by CRP or elsewhere • Risk is uncertain

SEABIRD ATTRACTION TO GALLEY WASTE AND DREDGE DISCHARGES • Expert caucus was advised that all benthic organisms would be discharged straight back to the sea floor and none would float • If this happens then this will not be a problem, unless accidents occur • The expert conferencing group (Issue 5) recommended all galley waste is returned to the mainland for composting

DEDICATED SEABIRD OBSERVERS • Expert conferencing group recommended independent trained observers on board the vessel to monitor and record seabird activity • In my opinion this should involve:  At least two observers, highly trained in seabird identification, density counts, seabird behaviour and recovery and documentation of seabird carcasses resulting from the mining operation  the first year of mining, and then a review

DEDICATED SEABIRD OBSERVERS • A training programme of at least four weeks duration (e.g. University of Canterbury Kaikoura Field Station in October) • I disagree that such work could as well be performed by partially-trained crew (with primary responsibility for other duties) • Such an approach has not been recommended for oil platforms or for the long-standing Scientific Observer Programme of MPI