TAN1116 voyage log - technical updates
Voyage updates from voyage leader Scott Nodder.
The voyage route can be seen in image on the right hand side - click to enlarge.
We have sailed thru Week 2 and a bit, including passing Station number 100. The weather has continued to be extremely kind to us over the last 10 days, although yesterday afternoon we had to curtail some deployments via the starboard crane because of 30-35+ knot winds.
We are about to complete the last 4 of the priority strata in the middle of the Chatham Rise, with deep (~1000 m - oreo and orange roughy environments) and shallow (~500 m - hoki/hake/ling environments) strata on the north and south sides of the Chatham Rise. There have been marked differences in the benthic fauna at the shallow sites, where crustaceans (galatheids, scampi, seriolid isopods, crabs) are important constituents, and echinoderms (urchins, holothurians, asteroids) and gastropods are prominent in the muddier sediments of the deep sites. The deep oblique midwater tows on the northern side of the rise have also revealed highly diverse fish communities, with many varieties of mesopelagic fish (viperfish, hatchet fish, eels, lightinghouse fish), as well as lantern fish, being caught. One targeted midwater tow on near-bottom acoustic marks at ~500 m caught a rich crustacean fauna of prawns and shrimps, which are important prey items for commercial fish from previous stomach analyses. We have also managed to get a full suite of day-night zooplankton net tows across the four strata from 30 m above the seabed to the surface. Euphausiids ("krill"), pteropods (sea butterflies) and copepods are more prominent in the middle of the rise compared to the salp-dominated fauna in the west. The calm conditions, we have been lucky enough to have over the last week or so, were exemplified by the development of a bright orange-red "red tide" (probably the heterotrophic dinoflagellate Noctiluca) a couple of days ago. The ship sailed through the 'red tide' which bioluminesed spectacularly in wake of the ship at night.
As of lunchtime 13 Nov, we have done 35 successful mesopelagic trawls (14 targeted midwater trawls and 21 oblique midwater trawls) for a total catch 686 kg made up of 147 species or groups. 7963 individual fish have been measured. Over the same timeframe, the benthic team have completed 22 beam trawls, 6 Brenke and 9 multi-corer deployments. The total number of stations by the end of today is 123, with at least a further 10 planned over the next 24 hours (dependent on weather).
14 Nov, Strata 7 & 8
We have finished off stratum 7, except for benthic and midwater trawls at site 7C. The deep oblique tows on the northern flank have turned up a rich diversity of fish fauna - lots of different mesopelagics and lantern fish. The beam trawls suggest a crustacean-dominated fauna (galatheids, crabs, scampi) at the shallow ~500 m sites, with heart urchins, polychaetes and holothurians important at ~1000 m sites on this northern flank.
Last night's multi-core station returned 30-40 cm long muddy cores from site 7A. Now passed station 100 (mesopelagic tow at site 7B overnight between 14-15 Nov), and have also completed sampling at two of the three stratum 8 secondary sites (8B and 8D), with core site 8A a focus today (16 Nov) and site 8C (and 7C) targets for the morning-early afternoon of 17 Nov - hopefully before the forecasted 40-50 knot SW blow comes through.
12-13 Nov, Strata 4 & 5
We are about to complete sampling at Strata 5, with a midwater fish trawl and a night-time zooplankton trawl to go before we head off to the north to Strata 7 overnight (5 hr steam). We have finished sampling in Stratum 4. On 12 Nov, we finished the night oblique midwater tows at sites 4F and 4B - mostly small midwater fish (myctophids, lighthouse fish, ribbon fish) before a day zooplankton trawl at 4A to complete sampling in Stratum 4. We then headed north to Stratum 5 (3 hr steam) and started off with a bottom (beam) trawl at site 5D. This was very muddy, with large gastropods (marine snails), hermit crabs, anemones, parasol urchins, shrimps, rattails, and some flatfish.
Overnight, the mesopelagic team managed to get around all the Stratum 5 midwater oblique tows in quick succession (at sites 5D, 5A, 5C and 5B) so we were able to pick up the outer benthic trawls at Site 5B (animals similar to site 5D) and at 5C (not muddy, abundant galatheid prawns, quill worms, shrimps, asteroids) in the morning.
We spent the rest of the day (13 Nov) at site 5A, which meant we were able to do conductivity-temperature-depth (CTD) sampling (for physical water structure, phytoplankton, bacteria and small zooplankton), the daytime midwater zooplankton (MOCNESS), benthic trawl (same at 5C) and a hyperbenthic invertebrate (Brenke) trawl just after dinner. We then went onto a midwater trawl (targeting near-bottom animals), followed by a night-time zooplankton trawl. After this deployment, in the early morning of 14 Nov, we will head north to strata 7 & 8.
11 Nov, Stratum 4
Over today, we worked on completing Stratum 4 with all the sampling except the day-time midwater zooplankton (MOCNESS) trawl completed at Site 4A and Site 4C and (hopefully) as the night progresses, sites 4B and 4F (oblique midwater fish trawls). The animals obtained from the benthic (beam) trawls in Stratum 4 have all been similar to others at this site, but very different to those over to the west, with Gracilechinus urchins (long-spined urchins) dominating the catches (>100 individuals, up to 350), hexactinellid (glass) sponges, orange Plutonaster asteroids and small holothurians (sea cucumbers), plus interestingly tiny carnivorous sponges.
The fish fauna has also been a bit different with much more diversity (lots of different mesopelagic fish and a reduction, thankfully, in the number of salps!). Midwater zooplankton tows also indicate some faunal differences compared to the east with euphausiids (krill) and pteropods (pelagic snails) becoming more prominent (though salps still dominate in the upper part of the water column). The sediment here is sand, and hard phosphorite and chalk pebbles, so only 4 multi-cores (soft sediment samples) in total from here (2 for macrofauna, 1 for meiofauna and sediment bacteria and 1 for sediment properties).
We will finish the remaining night-time oblique tows in Stratum 4 tonight (sites 4C, 4F and 4B) and the day zooplankton trawl at site 4A in the morning before heading north to start Stratum 5.
9-10 Nov, end Stratum 3 and start Stratum 4
We finished off Stratum 3 at about lunch-time on 9 Nov with the following:
Site 3F – Midwater oblique trawl which caught dogfish, myctophids (small midwater fish), salps, squid
Site 3C - Midwater oblique trawl which caught many small midwater fishes including lanternfish and viperfish
Site 3C – Benthic trawl - abundant brittlestars, cushion stars, large purple Tam O'Shanta echinoids, sea spiders, sponge, flatfish, rat-tails
Site 3F - Benthic trawl - abundant quill worms, salps, large purple urchins, rat-tails, eels, oreo, mysids, amphipods
Site 3A – Hyperbenthic trawl (Brenke sled) catching small invertebrates living about a metre above the sea bed.
We then had a 20 hr steam overnight to Stratum 4, arriving at 1430 h, 10 Nov, completing two mesopelagic fish tows on some unusual marks seen in the acoustic data at 400 m. These strange marks appeared to be almost 100% Hector's lanternfish (Lampanyctodes hectoris). Other strong acoustic marks at ~600 m were characterised by diverse fauna: salps, other small (myctophid) fishes, lighthouse fish, lantern fish, small squid.
We arrived at Site 4B and completed a benthic trawl which found abundant Gracilechinus (long spined) urchins, large and very small holothurians (sea cucumbers), large orange Plutonaster asteroids, sponges (including small carnivorous ones), corals and two small king crabs. Just before dusk, another beam(benthic) trawl was conducted at Site4F, returning even more long-spined urchins (5 fish bins full!), but in comparison to the previous trawl very little else.
We have just deployed the MOCNESS (midwater zooplankton trawl) at Site 4A, so will spend most of the day here tomorrow (11 Nov) doing all the night and day-time deployments at all the sites in Stratum 4 before returning for the final day-time zooplankton trawl on 12 Nov. We will then head north to do Strata 7 and 8 and return to Strata 6 if we have time.
8 Nov, Stratum 3
Had a great night and day set of deployments, with the first MOCNESS successfully completed last night at site 3A. We caught a few echinoids in the bottom net - just a little too close to the bottom! Also caught lots and lots salps in the top 200 m and copepods, amphipods and small bristletooth fish in the near-bottom nets.
We also completed all the other sampling at 3A:
- oblique midwater tow, CTD (conductivity-temperature-depth sensor) and beam (benthic) trawl . We found a diverse fauna dominated by lots of echinoderm varieties, seriolids and quill worms
- daytime zooplankton net (MOCNESS) - about 5 hours to run including set-up.
Our pelagic team are planning a mammoth night to get all the mesopelagic oblique tows at 3B, 3F and 3C completed by morning, so we can knock off the remaining beam trawls at 3C and 3F (and Brenke at 3A) during the day on 9 Nov. If we manage this, we will be heading towards Stratum 4 by late afternoon, arriving about 18-20 hours later in the early morning of Thurs, 11 Nov - possible rough weather also coming by then.....
Nov 7, end of Stratum 1 and start of Stratum 3
Overnight and this morning we completed Stratum 1 with a complete suite of sampling (except the 2 midwater zooplankton tows). Overnight, sites 1F, 1D and 1E were sampled with the oblique midwater fish trawl, found lots of midwater fishes, including myctophids, Rays bream, hoki, dealfish and >100 kg of salps at 1E, matching a SST change from 12 to 10 ºC, probably as we went across the Subtropical Front.
Interestingly, the three mesopelagic (midwater) tows we did prior to this sampling on 6 Nov, showed almost 100% dominance by certain mesopelagic fish. The final bottom trawl in Stratum 1 was completed at 1E, with large asteroids (Trojan starfish), quill worms, Flabellum corals, prawns, seriolids, sea spiders and salps, and a ghost shark, small catsharks and rat-tails in the fish fauna. We then headed down south to oreo country in Stratum 3.
Today (7 Nov) we did a benthic trawl at site 3B (large Tam O'Shanta echinoids, quill worms, red prawns, cod and salps), with a mesopelagic fish trawl at 400 m near to site 3A turning up Pyrosoma and other salps and a few myctophids. Tried one more mesopelagic fish tow, targeting acoustic marks at 750 m depth, but this shot had to be abandoned due to net fouling. We then mobilised ourselves for another go at deploying the midwater zooplankton net and it seems to be going well (hopefully!) as I email you now.
Approaching 50 deployments of gear on this voyage already, so all going well at this stage. Hope to finish off Stratum 3 by late evening 9 Nov or early morning 10 Nov before heading over to Stratum 4 (18 hour steam).
6 Nov, Stratum 1
By the end of today we should have finished Stratum 1 with a full complement of sampling.
We got zooplankton samples and also Brenke (benthic invertebrate) tows at sites 1A and 2A, which was good, helped immensely by the very calm weather and sea conditions (<1 m swell, 10-15 knot light N wind).
Overnight we are trying to get a full suite of oblique mesopelagic trawls at 1F, 1D and 1E (all matched with beam trawls; the latter at 1E to be completed tomorrow morning). After 1E we head down to the deep to Stratum 3, starting at site 3B, and working across to sites 3A, 3F and 3C over the next couple of days.
5 Nov, Core sites stratum 2 & stratum 1
Things are going well - all the sampling and preservation protocols seem to be working OK, and with the improving weather I hope that we will be through the deeper stratum 3 by the end of 9 Nov, so things seem to be on track.
The original 1C station was not in the depth ranges that we were after (400-600 m), which were down in an area of rough ground associated with a small canyon re-entrant , so we have picked a reserve station instead. We haven't tried our new gear – a benthic trawl with nets added on top to catch prawns and shrimps off the bottom – since it seems we are picking up enough of the larger prey items with the beam trawl by itself.
Stratum 2 Core
It's been a day of ups and downs today. We had issues overnight at site 2B, so we headed for site 2E and did the night-time oblique tow there.
We then started on the Core site at 2A, completing CTD (conductivity-temperature-depth sensor) and 3 multi-corer (benthic sediment sampler) deployments (to get enough sediment for all the analyses) at which point the sea and wind state meant that we weren't able to use the crane to move larger gear around the deck (30-35 knot NW winds), so these were aborted. We were still able to beam trawl and do some mesopelagic (midwater) tows until the sea state halted all other work until night fall at 2030 h.
We are now waiting for the seas to abate further before we can finish 2A with an oblique night-time mesopelagic trawl and a series of zooplankton net hauls to get some zooplankton samples.
Now planning on leaving 2A at about 0300 h 5/11/11 to start a series of benthic trawls at the secondary sites in stratum 1 (sites 1D, 1F and 1C), with work at site 1A hopefully starting tomorrow afternoon.
3 Nov - Stratum 2
Weather has been brilliant out here today and we have managed to get through most of the planned stations OK. Summary as follows:
- Station 1 Site 2D Beam (bottom) trawl - Sergestes prawns, galatheids, seriolids, juvenile Olivers rattails, started at 0700 h
- Station 2 Mesopelagic trawl (to look at acoustic mark) - L. hectorii, Rays Bream
- Station 3 Site 2F Beam trawl - Sergestes, crabs (C. victoriensis), galatheids, scampi, sea pens, conger eel, rattails
- Station 4 Site 2B Beam trawl - prawns, galatheids, echinoids, asteroids, quill worms, fan corals
- Station 5 Site 2B Mesopelagic trawl - underway as we speak,
We are hoping to complete Mesopelagic trawl tows overnight at sites 2D and 2F and start and complete the Core station at 2A tomorrow - will let you know how we get on! People seem happy to have got samples onboard and processed.