Fisheries and climate change – the big two marine problems go head to head this week. I couldn’t work out where some stories belonged, so if you are interested in either, scan both columns! My research for a talk in November on the Gulf Oil Spill is getting interesting, with (more) claims of independent research getting elbowed out of the way of a good legal battle! Sour grapes, or serious accusations? First though, something wholesome from the scientific journals:
A trans-antarctic seaway, Hoorah? The bryozoans living in the Ross and Weddell seas show significant similarities, despite living 1500 miles apart and separated by the West Antarctic Ice Sheet. The researchers hypothesise that there must have been an open seaway between the two (now isolated) populations, probably in the last inter-glacial 125,000 years ago. ScienceDaily (Aug. 31, 2010)
The early crustacean: Almost the entire life history of Precambrian organism, thought to be an ancestor of the crustacea, has been found in rocks in Dian, China. This is a nice research blog covering the main findings of an original publication in Nature. Deep Sea News, August 30th, 2010
Married for life (though we’ll never meet again): One problem facing the giants of the ocean is that chance encounters happen all too rarely. Whales get round this by having an organised annual get-together. The whale shark, however, seems to rely on these chance encounters, and this means that they may occur at a bad time for breeding, or too infrequently to maintain the population. To get round this lady sharks have a technique for storing sperm for long periods, and fertilising their eggs as they come ready. As a consequence the femal shark can be carrying several hundred embryos in different stages of development at one time – occasionally all from the one mating event! This breeding strategy makes the whale-shark especially vulnerable to fishing practices that selectively take the largest animals, as these are disproportionately important in the breeding stragegy for this fish. ScienceDaily (Aug. 31, 2010)
Crazy octopus: Thaumoctopus mimicus or the mimic octopus, takes the cephalopods camoflage abilities to new heights in mimicing other sea creatures – such as flatfish and sea-snakes – that help to deter predators. This article looks at the evolutional sequence for predator avoidance. ScienceDaily (Aug. 30, 2010). Previously we’ve picked up on video footage of the octopus mimicing a flatfish – at least four species of octopus are thought to use mimicry in this way to deter predation (previous post).
Land crabs on the march: The Christmas Island red crab (Gecarcoidea natalis) undertakes a migration each year during the wet season from their feeding grounds to the ocean to mate, a journey of several kilometres. To do this the crab has to make best use of its energy reserves, which it does by carefully regulating levels of a hormone called Crustacean Hyperglycaemic Hormone (CHH). ScienceDaily (Aug. 27, 2010)
Fisheries and exploitation
Unlucky horseshoe: Most of the decline in horseshoe crab numbers over recent decades is due to fishing for bait and the pharmaceutical industry. Future numbers are likely to be further effected, however, by climate change. The reasoning for this statement is not clear in the preçis in Science Daily, but apparently horseshoe crabs numbers have historically fluctuated with major climatic events. ScienceDaily (Aug. 30, 2010)
What I picked out from this was that a major user of horseshoe crabs is the pharmaceutical inductry – apparently ‘LAL’, which is extracted from the blood of horseshoe crabs is test of whether or not drugs, vaccines or medical equipment is surgically clean and free of bacterial contamination. Bacterial endotoxins can persist after standard sterilisation procedures, and cause fever. Previously these were screened out by injecting samples into rabbits. The crabs are collected, bled and then returned to the wild. Mortality in crabs going through the procedure (including capture) is estimated at between 10% and 15% of the total catch. More information, including some fascinating insights into the crab’s immune system at the Horseshoe Crab website.
Salmon declines: Recently there has been a reduction in the numbers of adult salmon in western North America. Salmon have evolved so that each stage in their life-cycle hitches a ride on a good food-source. In recent years, however, young fish (called smolts) have moved into the marine ecosystem too late to catch the spring phytoplankton bloom, and fewer individuals have survived to reach maturity as a result.
The earlier phytoplankton bloom is in response to warmer waters occurring earlier in the year – and may be an indicator of long-term climatic change (i.e. global warming). The salmon themeselves seem to be taking notice, however, and smolts are now tending to migrate earlier to catch the bloom.
Chittenden CM, Jensen JLA, Ewart D, Anderson S, Balfry S, et al. (2010) Recent Salmon Declines: A Result of Lost Feeding Opportunities Due to Bad Timing? PLoS ONE 5(8): e12423. doi:10.1371/journal.pone.0012423
Echinoderms likely to be the biggest sufferers: Echinoderms – starfish and their allies – lack a filtering system, such as a liver, for removing toxins from their bodies. As a consequence they are more at risk from environmental toxins, which they cannot get rid of once they have ingested them. Most at risk will be their microscopic larval stage, and significant die off here may disrupt a lot of the marine food web. Deep Sea News, August 30th, 2010
How not to run a scientific enquiry? There is some disquiet about the way that the scientific enquiry into the Gulf oil spill is being handled. Essentially the criticism is that research funding is coming either from BP, or being channelled into projects likely to support the US government’s litigation case. As a consequence the amount of independent scientific data may be limited. From Deep-Sea News, August 30th, 2010.
“Anger, depression, and helplessness”: Amongst the psychological responses to the Deepwater Horizon oil spill. ScienceDaily (Aug. 30, 2010)
Oil indicators in mangrove sediments: DNA analysis of micro-organisms (micro-eukaryotes) can be used to assess biochemical changes to the environment. In this study micro-organisms native to mangrove swamps in Rio de Janeiro were cultured in the presence and absence of oil. The amount of residual oil in the sediment after treatment, and genetic changes in the population were then both evaluated. In this study the fungi/metazoa were worst effected by the presence of oil, and that the diversity of sediment flora and fauna was impoverished by contamination. Diatoms, however, were seen to increase in abundance.
The authors speculate that their analytical technique may be generally applicable, though different sediments will have different microbial communities.
Santos HF, Cury JC, Carmo FL, Rosado AS, Peixoto RS (2010) 18S rDNA Sequences from Microeukaryotes Reveal Oil Indicators in Mangrove Sediment. PLoS ONE 5(8): e12437. doi:10.1371/journal.pone.0012437
PCBs in Aleutian fish: PCBs are seen generally to concentrate in fish higher up the food chain, but levels in all of the tested fish were quite high. Some fish were considered to pose a threat to human health if eaten as infrequently as ten times per year.
Hardell S, Tilander H, Welfinger-Smith G, Burger J, Carpenter DO (2010) Levels of Polychlorinated Biphenyls (PCBs) and Three Organochlorine Pesticides in Fish from the Aleutian Islands of Alaska. PLoS ONE 5(8): e12396. doi:10.1371/journal.pone.0012396
Geochip used for Gulf oil detection: “scientists found that microbial activity, spearheaded by a new and unclassified species, has degraded virtually all of the oil to undetectable levels without a significant level of oxygen depletion.” Magic? There is no supporting material in this report. ScienceDaily (Aug. 26, 2010)
Long-term spill effects: Anemones from coastal waters between Alabama and Louisiana are to be collected, and their state of health evaluated, in an effort to evaluate medium-term effects of the spill on wildlife in the area. ScienceDaily (Aug. 28, 2010).
Why are our efforts to combat climate change so pathetic? We beat the ozone hole problem, but I just don’t get the feeling that our climate policies as a species are making any headway. Every now and then we get the ‘big engineering solution’, like this one, which proposes sticking turbines in the Gulf Stream off the coast of Florida. The turbines will be tethered at a depth of 1200m – which is the same depth of the Deepwater Horizon. Unlike a marine oil field, however, the energy in an oceanic current is pretty diffuse (i.e. low-grade), but you have worse engineering problems (moving parts, maintenance, corrosion, fouling etc.). I’m not adverse to people taking a punt, but this is a serious problem, and if engineers have anything to say on it then they need to put together solutions that look workable, rather than aiming for a nice press release. From the BBC, 30 August 2010.
Whales in the carbon cycle: A small, though possibly significant, side-effect of whale fishing is the reduced ability of the world’s oceans to absorb carbon dioxide from the atmosphere. The world’s oceans are very efficient at recycling biological material, small plants and animals are quickly consumed, keeping the carbon they contain in the surface waters. Larger animals, however, like top predators and whales, sink quickly through the water column, and are likely to reach deep-sea bottom intact – taking their load of carbon with them.
If restored to pre-fishing levels, natural whale deaths would remove 1.6×105 tons of carbon from surface waters each year. A larger beneficial effect than many proposed climate-engineering projects.
Pershing AJ, Christensen LB, Record NR, Sherwood GD, Stetson PB (2010) The Impact of Whaling on the Ocean Carbon Cycle: Why Bigger Was Better. PLoS ONE 5(8): e12444. doi:10.1371/journal.pone.0012444