Category Archives: Ocean

Crushing predators reinvade the Antarctic benthos

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In Gotham, Batman drives a batmobile that shoots fire out the back and has all sorts of mechanical wizardry so he can catch fiends in style.  Or something close to that, unless my childhood was dreadfully misinformed.  He isn’t supposed to turn up in a St. Patrick’s day parade in New Jersey, pedaling away on a two-wheeled crime-fighting vehicle adorned with no fewer than 13 (count them!) bat symbols.  I feel that witnessing that would be strange–similar to the feeling you get when you discover your keys in the refrigerator next to the milk.  Simply out of place.

Recently, Antarctica has its own version of things showing up in the wrong place.  King crabs, predators that the Antarctic underwater shelf has not seen in over 40 million years, appear to be making a rapid comeback.  The endemic (unique to a specific, defined locale) nature of Antarctic shelf organisms is the result of a massive climatic cooling event in the middle Eocene, approximately 41 million years ago (Ma)1.  From 41 to 33.5 Ma, coastal sea surface temperatures decreased as much as 10°C, even before the onset on glaciation; this led to the eventual extinction of shell-breaking (durophagus) predators, such as modern bony fish, decapod crustaceans, and most sharks and rays. These groups have not returned due to their lack of an ability to physiologically cope with magnesium, one of the major cations present in seawater, at low temperatures.  Under one degree C or so, these magnesium ions are lethal to these organisms1.  Due to the fact that in the Antarctic, shallower seawater is slightly colder than that of the deep, they are effectively shut out of the shallows.

Distribution of epifaunal suspension feeders before and after the Eocene cooling at 41 Ma. The graph on the left shows temperature data derived from oxygen isotope values in bivalve shells. The schematic on the right shows the relative abundance of fossil concentrations of brachiopods, stalked and unstalked crinoids, and ophiuroids. Aronson et al. 2009, PLoS ONE.

Paleontological findings on Seymour Island, near the Antarctic Peninsula, reveal that dense populations of ophiuroids (Ophiura hendleri) and crinoids (Metacrinus fossilis and Notocrinus rasmusseni) were present on the soft substrate after the 41 Ma cooling event, but not prior1.  Both ophiuroids and crinoids are vulnerable to durophagy, and thus reduced predation pressure is implied after the Eocene cooling event.  This is quite straightforward:  if the things that normally eat you are no longer there, the size of your population increases, and you can invite the folks down the way to come over and watch Buffy the Vampire Slayer and enjoy your mean gin and tonics with a decreased sense of doom2.

Even today, these and other suspension feeders are abundant across the Antarctic shelf3.  However, in the past 50 years, sea surface temperatures off the Antarctic Peninsula have risen 1°C4, and as a result, predatory crabs and duropaguous fish may be able to enter this isolated shelf environment.  Anomuran king crab populations have already been found in slightly warmer, deeper waters nearby5 and it was reported on Sunday by the Washington Post that a recent expedition observed hundreds, potentially primed for invasion into the shallows of the continental shelf.  Dr. Sven Thatje and colleagues are currently searching thousands of seafloor images for evidence that predation by these crabs is ongoing.

Current climatic warming is essentially opening a physiological door for these polar predators to reclaim their place in the Antarctic benthic community via range extensions and human-induced introductions5.  This reinvasion has the potential to drastically alter ecological relationships, perhaps even eliminate populations of dominant suspension feeders and homogenize the unique Antarctic nearshore benthos with higher latitude communities.

Images/figure:  1) Michael Bocchieri/Bocchieri Archive, from Flickr user Foto Bocch (cc).  I have been itching to find an excuse to use it since I saw it as NPR’s photo of the day. 2) From Aronson et al. 2009, PLoS ONE (cc).

1. Aronson RB, Moody RM, Ivany LC, Blake DB, Werner JE, & Glass A (2009). Climate change and trophic response of the Antarctic bottom fauna. PloS one, 4 (2) PMID: 19194490
2. I’m actually unaware of any invertebrates that enjoy Joss Whedon shows or G and T’s.  Pity for them.
3. GILI, J., ARNTZ, W., PALANQUES, A., OREJAS, C., CLARKE, A., DAYTON, P., ISLA, E., TEIXIDO, N., ROSSI, S., & LOPEZGONZALEZ, P. (2006). A unique assemblage of epibenthic sessile suspension feeders with archaic features in the high-Antarctic Deep Sea Research Part II: Topical Studies in Oceanography, 53 (8-10), 1029-1052 DOI: 10.1016/j.dsr2.2005.10.021
4. Clarke, A., Murphy, E., Meredith, M., King, J., Peck, L., Barnes, D., & Smith, R. (2007). Climate change and the marine ecosystem of the western Antarctic Peninsula Philosophical Transactions of the Royal Society B: Biological Sciences, 362 (1477), 149-166 DOI: 10.1098/rstb.2006.1958
5. Thatje, S., Anger, K., Calcagno, J., Lovrich, G., Pörtner, H., & Arntz, W. (2005). CHALLENGING THE COLD: CRABS RECONQUER THE ANTARCTIC Ecology, 86 (3), 619-625 DOI: 10.1890/04-0620

Frontiers: The deep sea and climate

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When we think about climate change and the ocean, many minds turn immediately to images of shallow-water corals, bleached white from the lack of zooxanthellae (internal, photosynthetic symbionts), driven away by heat and other types of stress.  However, the consequences of an increased atmospheric CO2 reach much deeper into the ocean.  The global ocean has an average depth of 3800 meters and comprises 71% of the total area of Earth, making the deep-sea far and away the largest biome on this planet.  In terms of volume, the deep-sea pelagic—the water-column itself—contains over a billion cubic kilometers of seawater.  Less than 5% of the deep benthos (the seafloor) has been remotely sensed, and less than a hundredth of one percent has been observed directly, sampled, and studied.  Even so, species diversity in the deep-sea is among the highest known1.

As a society, we still collectively get excited about the discovery of new species. And we should—such discoveries are essential to science.  The public being interested in new species is also quite importance for the continued funding of exploratory research.  Since 1840, 28 new habitat or entire ecosystems have been discovered in the deep ocean.  Not simply new species, but entirely new environments. Cold seeps, hydrothermal vents, brine pools, xenophyophore fields, just to name a few—these are all habitats that have only been known since the 1970s1.

Year of discovery of new habitat/ecosystem in the deep sea since 1840 (Ramirez-Llodra at al. 2010)

However, the lack of taxonomists to classify and describe the new species in these novel habitats dampens the spirit of discovery somewhat—specimens languishing in collections, as of yet unidentified due to the lack of support for specialists, harkening back to the last, frustrating scene in Raiders of the Lost Ark.

Atmospheric carbon dioxide concentrations are predicted to exceed 500 ppmv before 21002,a value not seen in the past few million years3.  This is contributing towards both warming and ocean acidification4,5.  It is uncertain how benthic organisms and their associated ecosystems as a whole will react; particularly little is known regarding the effects of climate change in the deep-sea. Continue reading →

Sea debris: shipping containers and marine life

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Approximately 10,000 shipping containers tumble off into the sea every year, bobbing around for a bit before, in most cases, sinking into the deep ocean.  To discover what happens to these containers after reaching the seafloor and what potential effects these abrupt structures may have on marine communities, the Monterey Bay Research Institute is teaming up with the Monterey Bay National Marine Sanctuary to investigate the biological community found on a shipping container offshore of California.  The benthos in much of the deep-sea, including the vast abyssal plains, is primarily composed of sediment.  These containers could suddenly provide hard substrate in an environment that usually lacks it, altering the habitat’s physical characteristics and possibly changing the suite or abundance of species present.  Researchers will be using a remotely-operated vehicle to compare sites at different distances from the shipping container, which is under about 1,300 meters of seawater.

Fittingly, the funding for these research cruises came from a settlement between  the National Oceanic and Atmospheric Administration and the shipping company whose vessel lost this specific container and 14 others in 2004.  The discovery of this container (chock-full of 1,159 steel-belted tires) lends an important opportunity to study the impacts of this global issue.

Read the MBARI press release here (via Ed Yong on Twitter).

Image: runner310 on Flickr (cc)

An octopus that can do impersonations

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A human mimicking another human is impressive, especially when it’s done well.  But the octopus Thaumoctopus mimicus mimics members of other taxa, such as sea snakes and fish, as a defense mechanism.  Maybe it should get a spot on Inside the Actor’s Studio too.

[The above video is from the California Academy of Sciences, cc]

The future of shallow-sea coral reefs

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Coral reefs, in case you haven’t been keeping up, are increasingly threatened by overfishing, ocean acidification, and warming, among other human-derived factors.  Recently, much buzz has been created on the web (e.g., here, here, and here) in the wake of an updated assessment from the World Resource Institute and its partners concerning the global status of shallow-sea coral reefs.

I confess I have not had the chance to dive into the full report, but here are some key snippets from the  executive summary:

  • 60+ % of the world’s coral reefs are threatened by local sources, such as overfishing, destructive fishing methods and pollution
  • Overfishing is the “worst immediate threat,” affecting 55% of reefs.  Coastal development and land-based pollution, and maritime pollution and damage from vessels come in second and third, affecting 25% and 10% of reefs, respectively.
  • 75% of shallow-sea coral reefs are threatened by the aggregation of local and thermal stresses.
  • Despite that 25% of reefs are within protected areas, many of these are inadequate or only partial protected.

The report also offers map-based information for the current status of these ecosystems and predictions for 2030 and 2050, integrating both local and global threats.  WRI offers KLM files of these assessments/probable future scenarios here, which I quickly threw into Google Earth and centered the maps over southeast Asia, generally acknowledged to the ‘epicenter of marine diversity’.  Click on the images to embiggen; the cool-colored dots represent sites with low risk and the red – maroon dots represent sites that are increasingly threated1.

Today

 

2030


2050


Visit the World Resources Institute to check out the report, the summary, map files, and lots more (cc 3.0).  The executive summary also has a nice list of ways you can help.

 

 

1 If anyone knows how to import .kmz files into the far more figure-friendly Google Maps without wading into the land of ESRI and QGIS, and is willing to share, that would be excellent.

 

 


Distinct communities on a Tyrrhenian seamount

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Using a Remotely Operated Vehicle, researchers surveyed a large seamount in the Tyrrhenian Sea off the coast of Italy, finding three distinct biological communities.  Seamounts, undersea mountains, can hugely affect the way water flows in an area and can provide hard substrate for benthic animals.  These features are generally acknowledged to be potential hotspots in terms of how many species are in a given area (known as species richness).

Marzia Bo and colleagues1 detail the the species composition of the Vercelli Seamount in a paper appearing in PLoS ONE.  Similar to other Mediterranean seamounts, the  relatively shallow summit of Vercelli hosts kelp  and algal-dominated communities at the very top (60-70 meters depth).  A bit further down, from 70-80 meters, the southern flank of the seamount hosts mostly organisms that are well-suited for a high-flow environment, such as octocorals. Species found on the northern flank are adopted for lower-flow regimes and feed by active filter-feeding, for example, sponges and ascidians.

The study of seamounts, these seemingly esoteric oceanic peaks, is still very exploratory due to the difficulty in sampling in the open and deep ocean.  Only a few hundred seamounts have been sampled biologically out of the estimated hundreds of thousands or millions thought to be present in the global ocean2. This work illustrates that seamounts can consist of multiple habitats over relatively little area. This is likely due to the different environmental conditions that are created by the feature itself, such as varying hydrodynamics (especially relevant here, with active and passive filter-feeders grouped), as well as slope and depth gradients.   Bo et al. note that the conservation value of Vercelli should be focused on the variety  of different communities the seamount supports and the diversity of life contained therein.

Though a seamount may have the impression of being remote and singular, the total global area represented by large seamounts is roughly equal to the size of Europe and Russia combined.  This estimate is actually quite conservative and only takes into account seamounts with greater than 1500 meters in relief3.

This is an open-access paper; read the original work here.

The figures shown above are from Bo et. al. 2011 (cc).


Sources:

1. Bo M, Bertolino M, Borghini M, Castellano M, Covazzi Harriague A, Di Camillo CG, Gasparini G, Misic C, Povero P, Pusceddu A, Schroeder K, & Bavestrello G (2011). Characteristics of the mesophotic megabenthic assemblages of the vercelli seamount (north tyrrhenian sea). PloS one, 6 (2) PMID: 21304906
2. Wessel, P, Sandwell, DT, & Kim, SS (2010). The global seamount census Oceanography, 23 (1), 24-33
3. Etnoyer, PJ, Wood, J, & Shirley, TC (2010). How Large Is the Seamount Biome?Oceanography, 23 (1), 206-209

Lunar cycles and reproduction in the deep sea

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Some biological patterns in marine species, particularly concerning reproduction, are related to the moon.  Shallow-ocean corals, for example, undergo mass spawning events (the synchronous release of eggs and sperm into the water column to combine), the timing of which, are set to the lunar clock.  Reef fishes, shallow-ocean echinoderms, mollusks and more, also time spawning events in respect to the phase of the moon.

The deep-sea, the largest biome on Earth, covering more than 326 million km2, has not been explored in terms of this lunar-synchronicity.  The dearth of photosynthetically-useful sunlight below 200 meters* would appear to make such moonlight-related cycles unlikely at best.

However, in a recent paper, Annie Mercier and her colleagues have shown that this may not be the case.  They demonstrate in both lab and field settings evidence of lunar periodicity in the reproduction of 6 deep-sea species, containing members from two different phyla:  Cnidaria and Echinodermata.

The researchers examined preserved samples of Phormosoma placenta (a deep-sea echinoderm) collected at various stages of the moon.  They found that despite being collected from between 700 – 1400 meters beneath the waves, physiological signs of recent spawning in both sexes coincided with the new moon.

Back in the lab, gamete and larval releases (reproduction events) were observed in captive specimens from 5 different species according to lunar patterns.  These specimens were collected between 100-1000 meters, with most species collected below 400 meters.  A minimum of 3 lunar months’ worth of data was compiled; some species actually repeated breeding periods in this timeframe.

The question remains if these animals are displaying internal rhythms that are kept in time by some sort of lunar cue, or if they are responding to something externally that follows the lunar period.  But what cues, or drivers, of a lunar period could be detectable at such great depths, where even sunlight wanes or is essentially eliminated?

Organic matter from surface waters falls into the deep sea; there is the possibility that these fluxes of sustenance may show lunar patterns.  Previous work has shown growth bands in some species of deep-sea corals that may correspond to monthly or lunar periods.  Other hypotheses include the idea that these animals can somehow directly perceive moonlight at great depths, or that deep tidal (related to lunar phase) currents exist.

In this study, internally brooding corals released larvae during the full or during the waning phase.  The 4 free-spawning species released gametes with the new moon.  The authors note that while this is opposite to the mass spawning events in shallow-ocean corals, which release during the full-moon, this may be due to the very different environmental and biotic factors in shallow areas versus the deep sea.

 

* This is the reason that little to no primary production occurs (that is, organisms producing chemical energy) in most, but not all, ecosystems known in the deep-sea.  Some deep-sea organisms are capable of undergoing chemosynthesis and can use inorganic chemicals, rather than sunlight as in photosynthesis, as an energy source.  However, even with a widespread lack of primary productivity and severe food limitation in most areas, diversity in the deep sea is among the highest on the planet.

Image:  Flicker user ZedZap (cc 2.0)

Sources:
ResearchBlogging.orgMercier A, Sun Z, Baillon S, & Hamel JF (2011). Lunar rhythms in the deep sea: evidence from the reproductive periodicity of several marine invertebrates. Journal of biological rhythms, 26 (1), 82-6 PMID: 21252369
Ramirez-Llodra E, et al. (2010). Deep, diverse and definitely different: unique attributes of the world’s largest ecosystem Biogeosciences, 7 (9), 2851-2899 : 10.5194/bgd-7-2361-2010

Bottom Trawling Banned in Belize

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On December 8th, Belize signed legislation into place that bans bottom trawling in the nation’s entire Exclusive Economic Zone (out to 200 nautical miles).  Oceana (press release), an international organization focused on ocean conservation, assisted the government by negotiating the buyout of existing trawlers; this action also received the full support of the Belize Fishermen Association.

Bottom-trawling has long been compared to its terrestrial analog of forest clear-cutting1. Imagine your local forest bulldozed in order to collect a single target species; not only is the suite of animals and their diversity enormously changed, but their habitat is largely destroyed.  However, this happens on an enormous scale in the global ocean, and in the vast majority of cases, is totally legal due to the lack of an international moratorium on trawling and far too few marine protected areas.  Fishing gear dragged along the benthos can crush and bury marine animals, utterly decimating structure-forming organisms, such as sponges or corals, which provide habitat.  The size, diversity, and turnover time of dominant species are reduced, leading to highly-altered community structure, which can persist for decades.  Trawling is not a series of isolated incidents but affects immense areas.  For example, off New England and in the Gulf of Mexico in the U.S., the total area fished by trawling is 138,000 km2 and 270,000 km2, respectively, with many areas being swept more than once per year2.

Trawling is a devastating, non-selective fishing method that adds to the global issue of overfishing and obliterates biologically-produced habitat.  Trawling impacts are visible from space.  In a recent study assessing the impact of human activities on the deep ocean in the North East Atlantic, researchers found that the spatial extent of bottom trawling is, conservatively, at least an order of magnitude larger than all other quantified activities combined, including dumping, communication cables, the hydrocarbon industry, and research activities 3.

This action by Belize should set an example to all coastal nations, and hopefully represents a small step towards comprehensive legislation in both national and international waters.  Belize’s ban goes into effect December 31, 2010.

 

1.  Watling L, Norse EA (1998) Distrubance of the seabed by mobile fishing gear:  a comparison to forest clearcutting. Conservation Biology 12: 1180-1197

2.  For review see:  Jackson JBC (2008) Ecological extinction and evolution in the brave new ocean. PNAS 105: 11458-11465

3. Benn AR, Weaver PP, Billet DSM, van den Hove S, Murdock AP, et al. (2010) Human Activities on the Deep Seafloor in the North East Atlantic: An Assessment of Spatial Extent. PLoS ONE 5(9): e12730. doi:10.1371/journal.pone.0012730

Image:  Great Blue Hole, Belize–part of the Belize Barrier Reef Reserve System World Heritage Site.  USGS, Wikimedia Commons.