Hello. My name’s Will. I’m one of the marine ecologists on this trip and about to start my PhD at Newcastle University. I’m here to examine deep sea food webs on ocean ridge systems. To do this I’m heading to two very remote locations in the world- East Scotia Ridge (ESR) in the Antarctic and to the Mid Atlantic Ridge (MAR). These sites are very different and have been chosen for very special reasons. The sites on the ESR are hydrothermal vents while the stations selected as part of the ECOMAR programme are areas that are believed to contain none or limited hydrothermal activity.
So, my first stop is here over the MAR with my samples approximately 2500 metres below me. That is the equivalent of 25 football pitches or 7.5 Eiffel Towers. Which begs the question how am I going to get at them? Well, I’m going to be collecting material in two different ways. Firstly with the semi-balloon otter trawl (OTSB) during the first three cruises and secondly the UK’s deep sea remotely operated vehicle ISIS on the final cruise in 2009. These two pieces of equipment will allow me to collect different types of animals. The OTSB captures mobile megafauna that live on the sea floor, and has been written about in previous blog instalments, while ISIS will collect suspension feeders that live in areas that the OTSB cannot reach- mainly attached to rocks and steep surfaces. Once the catch is on board and sorted, a small tissue sample is removed from the specimens, which I will take back to Newcastle for biochemical analysis. This will give me an idea of the position or trophic level of each species within the food web. Ultimately, I will compare the food webs of the MAR (non-vent) and the ESR (vent) to determine the relative importance of chemosynthetic and photosynthetic sources of energy at vent sites under strongly seasonal and very productive waters in the Antarctic, and examine the range of influence and incorporation of chemosynthetic energy into the food-webs of ‘non-vent’ ridge fauna at the MAR.
For now we are still on the CTD transect, heading north, which means no sampling for me. But as the blog has already mentioned there a series of scientists who are currently working around the clock. Andy wrote about the work Jane Read from NOC was conducting in relation to the CTD transect yesterday. So today I’m going to write about the work currently being undertaken by the scientists from Plymouth Marine Laboratory (PML). Their current aim is to collect data that will validate ocean colour satellites. Ocean colour is literally the colour of the sea, which is caused by whatever is in the surface layer that absorbs light. In the open ocean the main absorbing particles are phytoplankton (Fig. 1) or in other words the plants of the ocean. There are millions of these in a single droplet of sea water. So in the upper 100 metres you have a dense forest of phytoplankton which collectively are bigger than the tropical rainforest. Phytoplankton forms the base or foundations of the food web. They capture the energy from the sun and use carbon dioxide (CO2) to produce their own food in a process known as photosynthesis. This energy is passed to the next level when they are eaten by zooplankton and so on up to higher levels of the food web to animals like fish and whales.
The phytoplankton can be observed form space by ocean colour satellites. There are currently three ocean colour satellites that orbit the earth. These are SeaWIFS, MODIS and MERIS (Fig 2). When sunlight shines on the sea a proportion is absorbed by the phytoplankton and some of it is reflected back to these satellites. Each satellite carries a radiometer that can detect sunlight reflected from the sea surface. From this signal the scientists are able to get an idea of the amount (or biomass) of plant life in the oceans. They can compare these satellite images of phytoplankton biomass against sea water samples collected by the CTD rosette (mentioned in Colin’s blog). Phytoplankton plays a crucial role in regulating the earth’s atmosphere. Their role can not be understated as they absorb more carbon dioxide (CO2) from the atmosphere than land plants. Therefore, phytoplankton plays an important part in regulating CO2 concentrations and in turn our climate.
The guys form PML are also conducting experiments on the photosynthesis and carbon fixation by phytoplankton. Using light, phytoplankton biomass and sea surface temperature, which can be derived from satellite data, they are able to produce global maps of carbon fixation by the phytoplankton and compare this with the experiments that are done on board. Satellite measurements of carbon fixation are being used to monitor the health of the oceans and how much CO2 phytoplankton is drawing down from the atmosphere. These measurements are crucial in understanding the seas role in reducing global warming.
So for me I’m going back to reading scientific papers, books and watching DVDs until I get a chance to start fishing once more! And finally a big HELLO to all my friends and family back home. See you all soon.
PS Did you know that a cod cannot hear the James Cook when she passes 20 metres above it!