Beautiful intruders: the misplaced lionfish

Lionfish (Pterois volitans and P. miles) populations have drastically exploded in the western Atlantic and the Caribbean in the past decade, and not without attracting some attention. The trouble is that these gorgeous fish sporting an array of venomous spines are invasive species.  They naturally occur in the Indo-Pacific but have been introduced to Florida via aquarium releases and are now potentially causing significant changes to marine ecosystems, the inhabitats of which have not evolved with this fish.  They can now be found from Costa Rica and Venezuela up the US eastern seaboard to Rhode Island, a truly impressive extent considering the first individual was found offshore of Florida in 1985.  Recently, I was fortunate enough to dive in Roatan, Honduras on my honeymoon and lionfish were a relatively common sight, despite their efforts to hide among the barrel sponges on the benthos.  They could potentially spread well into the southern hemisphere, along the the coast of South America, based on the lethal minimum water temperature [pdf] for this fish (10 C).  Lionfish feed upon the larvae of reef fishes, undercutting the next generation of fishes.  They can spawn year-round and release buoyant egg masses that can float in the currents for weeks, ensuring a wide distribution.

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Crushing predators reinvade the Antarctic benthos

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

Distinct communities on a Tyrrhenian seamount

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

Ecologists…helping to thwart the next banking crisis?

Making sense of the relationship between the individual and the system is one of science’s oldest challenges. What might be new to banking is well-studied in biology, for example. This prompted Bob May, ecologist and former government chief scientific adviser, to approach the governor of the Bank of England Mervyn King with an offer of help and advice. Could there be, he wondered, any parallels between banking and ecosystems?

The main idea here seems to be that banking systems would do well do mimic ecosystems, in which the diversity of species and stability tend to go hand in hand.  Read more at the Guardian (link below).

via Scientists of the Subprime: Can biologists avert another banking crisis? | Ehsan Masood | Science | guardian.co.uk.

The need for geophysical conservation

How should we go about managing the conservation of biodiversity in the face of a changing climate?  Species by species?  Seems tedious.  And expensive to carry to completion.  Wouldn’t it be easier if we could determine what factors contribute to high species richness in a non-abstract way, find areas with those parameters, and start there, in terms of protection measures?  A new study in PLoS ONE by Drs Mark Anderson and Charles Ferree, both of The Nature Conservancy, is a step towards this.  The majority of conservation plans do not account for shifts in species distributions resulting from climate change; the authors posited that if some combination of large scale, geophysical variables, such as elevation or local geology, predicted species richness independently of climatic variables, then ecological reserves could be created that function to protect a large number of species in current and future climate scenarios.

Study area with overlaid geology classes (Anderson and Ferree 2010)

Using geology, elevation, species, and climate datasets for a section of the northeast US, combined with the Maritime Provinces of Canada, the researchers ran linear regressions in search of a model in which non-climatic factors predicted species richness, and did not show dependence on climate.  They found that the number of geology classes (like acidic shale or fine sediment), latitude, elevation range, and the amount of calcareous bedrock produced a non-climate dependent model with an R (sq) of 0.94—meaning that the model accounts for 94% of the variance in the species diversity among these states/provinces.

Anderson and Ferree 2010

That’s a stunningly significant statistical value, especially considering that this study concerns itself with an area that’s roughly twice the size of California.  When the 13,500 + species were split into their respect taxa, the model performed well.  During geographic analysis, 40% of rare species within this area were shown to be constrained within 1 geology class; 61% of rare species were constrained in two classes, further making the case of a species and geology class relationship.  In a further test, rare species were distributed non-randomly among geological classes—so some classes were associated with higher densities of rare species than others.  These results also show that habitat—in this case geophysical—heterogeneity may be more important than the size of the area surveyed (when no relationship exists between area and heterogeneity) in determining the number of species.

This study sets the stage for conservation approaches associated with geophysical settings, but also stresses scale is an issue—entire functioning ecosystems would need to be protected, not just bits of heterogeneous geology here and there.  However, this is a long-term strategy that may be successful in biodiversity conservation in a changing climate, and will not necessarily prevent specific species extinctions.  Species specific and geophysical conservation approaches could of course be combined, but the authors realistically expect that “inevitable tradeoffs” between these efforts in a period of rapid climate change should be expected.  Scale and connectivity between species’ geophysical environments are more important than before realized.

Images:  PLoS ONE makes figures and articles available under a Creative Commons attribution license.

ResearchBlogging.org

Anderson, M., & Ferree, C. (2010). Conserving the Stage: Climate Change and the Geophysical Underpinnings of Species Diversity PLoS ONE, 5 (7) DOI: 10.1371/journal.pone.0011554