Editor’s Selection IconWell I haven’t done a Research Blogging post in a very long time. But I was inspired by this news release I read today about crabs spilling onto the Antarctic peninsula with warming waters. On a recent voyage to Antarctica, marine biologists collected digital images of these deep water predators moving closer to shallow coastal waters which have been excluded from for potentially millions of years, because the shallow coastal waters, until recently, have been too cold to support these predators. This can be devastating to the coastal shelf community in Antarctica, which has adapted no defenses in the absence of these predators – many organisms here have thin shells or don’t burrow into sediments.
My friend and fellow Southampton College alum, Molly, recently blogged about this issue. She is currently doing graduate work at the University of Alaska Fairbanks on snow crabs, so she loves crabs (as her blog title suggests). The idea is that, as the above article states, these crabs are moving closer to the Antarctic shelf, and this can have devastating impacts on the local fauna there. It was highlighted in a National Geographic article in 2008.
According to research, the Antarctic coastal shelf experienced a cooling trend starting around 40 mya, and the waters, due to the cooler temperatures, essentially became devoid of many types of predators. The subsequent community had evolved over those millions of years in the absence of major durophagous predators – known for their shell crushing abilities. The major predators in these bottom waters are slow moving invertebrates, and the community developed over time accordingly. Now as surface waters are warming, crabs are able to enter these new areas from the depths, and can have potentially harmful impacts.
At first, this might seem counter-intuitive – typically bottom waters, and the deep ocean, are very cold, and the water warms as you get shallower. This is not the case on the Antarctic shelf, where the shallow waters are actually colder than the surrounding deep waters. This is due to the cold Antarctic circumpolar current, which runs clockwise around Antarctica, isolating its cold water and continental shelf from crabs and fish with bony jaws.
However, the absence of crushing predators was not due to geograhic isolation of the Antarctic continental shelf (although Antarctica is oceanographically isolated, the barriers of biological invasion in this case are physiological, according to Richard Aronson, professor of biology at the Florida Institute of Technology, and others in 2007). Physiologically, the crabs are unable to process magnesium in their blood at the normal shelf water temperatures, resulting in narcotic effects. So the crabs, for millions of years, had stayed away. The resulting shelf community, consisting of epifaunal suspension feeders, lacked the typical defense mechanisms seen in other benthic environments where soft bottom bethos have been evolving with predators in an evolutionary arms race. As already mentioned, the archaic communities of the Antarctic shelf, consist of animals with thin shells which don’t burrow. So one could imagine that if these crab predators were allowed to move into these coastal waters, it could have devastating consequences on the community there.
This is not a crab you would encounter in the Antarctic, however, it is as close a figure to the "arms race" - crab claws, thick clam shell - as I could find on the interwebs.
Range expansions are something that are particularly interesting to me. The lifting of physiological barriers due to temperature will allow biological invasions of numerous species. How these species interact with native species is of great concern. In particular, predator-prey relationships between novel predators and naive prey can restructure communities in warming oceans. Despite its perceived isolation, this research suggests that Antarctica will not be immune to these impacts (and it fact, polar regions are likely to experience a greater magnitude of temperature change).
And the real news here, is not only is there evidence the crabs are moving closer to these shallow shelf communities, but that it is occurring at a much more rapid rate than anticipated.
A quote by Dr. Aronson from the new article: “If you look at the warming trends on the peninsula, you would expect that the crabs would come back in 40 or 50 years,” Aronson said from his office in Melbourne, Fla. ”But boom, they’re already here. This is the last pristine marine system on Earth and it could get destroyed”.
This is big and bad news for the Antarctic bottom communities. Clearly, this is something that should be monitored closely. But it is not in any means an Antarctic phenomenon. In many regions where warming is taking place, range expansion of novel predators can occur. This is something all benthic communities could experience in the near future.
Aronson, R., Thatje, S., Clarke, A., Peck, L., Blake, D., Wilga, C., & Seibel, B. (2007). Climate Change and Invasibility of the Antarctic Benthos Annual Review of Ecology, Evolution, and Systematics, 38 (1), 129-154 DOI: 10.1146/annurev.ecolsys.38.091206.095525
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
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
Thatje, S., Hall, S., Hauton, C., Held, C., & Tyler, P. (2008). Encounter of lithodid crab Paralomis birsteini on the continental slope off Antarctica, sampled by ROV Polar Biology, 31 (9), 1143-1148 DOI: 10.1007/s00300-008-0457-5
Because I couldn't have a climate related article without citing the Church of the Flying Spaghetti Monster
Recently, a few articles started appearing about the dramatic loss of oysters throughout the world, and how in many areas, they are “functionally extinct.” The article from ScienceBlogs talks about the findings of an international research team lead by Dr. Mark Luckenbach of the Virginia Institute of Marine Science. In over 70% of the 144 estuaries studied, current oyster levels are at 10% or less of historic levels. They estimate that over 85% of the world’s oyster reefs have been lost. The amount of loss exceeds any other shallow water benthic marine habitat that has been similarly studied. Obviously, this can cause problems.
The Underwater Times article mentions the term “functionally extinct” when referring to current oyster populations – that in some areas, oyster populations are less than 1% of historic levels, mainly due to overharvesting, disease, and invasive species introductions. But what does “functionally extinct” mean? In this sense of the term, it is when a species experienced such a reduced population that said species no longer plays a role in the functioning of an ecosystem. Obviously, the loss of any players in an ecosystem can be devastating. But oysters are a foundation species, providing a variety of ecosystem functions that renders them more important to their estuarine ecosystems than many of the other species. Oysters create biogenic 3-D structure in the forms of reefs, which build up from the seafloor and in many locations emerge from the water, particularly at low tide. This structure provides a plethora of microhabitats and niches for a variety of species to live. In addition, since oysters are filter feeders, they play an important role in nutrient cycling in estuaries, packaging things in the water column (plankton, particulates) and delivering them to the bottom where they are consumed and utilized. During this process, oysters actively clear the water column, increasing light penetration to the bottom and potentially allowing valuable submerged macrophytes to grow, adding structure to the reef and surrounding area, creating even more habitat. A number of species depend on this habitat for food ad shelter, as they are valued nursery and feeding grounds for numerous estuarine species. This function is vital to fisheries, as many finfish spend a portion of their lives foraging around oyster reefs. So when the articles suggest that oysters are becoming functionally extinct, it has serious repercussions for the ecosystem as a whole.
Clearly, the loss of oyster reefs are problems both economically and ecologically. However, some research suggests all is not lost. Stricter harvesting laws, fewer baymen, and no-take sanctuaries have helped maintain oyster populations, albeit low populations, in some areas. Better and more successful management is the first step towards saving oysters, and the report made the following suggestions for restoring and maintaining oyster reefs:
The prohibition of harvests where oyster populations constitute less than 10% of their prior abundances, unless it can be shown that dredging and other harvest methods do not substantially limit reef recovery.
New thinking and approaches to ensure that oyster reefs are managed not only for fisheries production but also as fundamental ecological components of bays and coasts that provide invaluable ecosystem services.
Steps to ensure that harvests, particularly those carried out by dredging, do not damage the remaining reefs.
Regular monitoring of reef conditions.
There is plenty of other relevant information out there about oyster reefs, research, and the issues facing them. I particularly recommend the blog In the Grass On the Reef, which focuses on research underway by Florida State researchers on salt marshes and oyster reefs. In particular, they update posts about their research in ways which are easy to understand with great visual aids including photos and videos. Definitely check that one out.
A clump on barnacles on one of my cinder blocks in Shinnecock Bay, NY
If you ever needed to know one thing about barnacles, its that they have large penises. Sure, you might be thinking barnacles are so small. But relative to total body size, they have the largest penises. It is a result of living a sessile life, remaining attached to the spot which they settled as larvae. Since they are unable to move to mate, they had to develop a different strategy. Hence, the large penises.
Former Stony Brook University Department of Ecology and Evolution student J. Matthew Hoch (now at the Southeast Environmental Research Center at Florida International University) spent his time here researching barnacle penis morphology. Some of his findings were published in the most recent issue of Marine Biology.
Some of his interesting findings were that both wave action (yes! the motion in the ocean… this makes SO much more sense to me now) and population density can have significant impacts on penis morphology. His study organism, the Atlantic acorn barnacle, Semibalanus balanoides, is known to have a penis with a exoskeleton with “accordion-like folds” that allows it to stretch to many times its relaxed length in order to find a mate. This is useful due to their sessile lifestyle, and makes copulation with their neighbors much easier.
What Hoch found was that population density has an impact on overall penis length. Barnacles which were sparsely populated had more of the folds in the penis, indicative of having a greater fully stretched length. This is presumably an adaptation to low population densities, allowing for the chance of successful mating. Those barnacles in crowded conditions had fewer folds, indicating that they are likely to have less ability to stretch (and also less need to do so).
And now the motion in the ocean part. Barnacles on wave exposed shores grow larger and their penises grow thicker/wider. They aren’t necessarily longer than those that live in protected sites, nor do they have more folds allowing them to stretch greater distances. They just have thicker penises. This is likely a result of the water action. These barnacles have to have thicker penises for more support, making them less likely to break in the wave action and more likely to produce successful mating attempts.
All in all, it was an interesting read, seeing how barnacles adapt reproductive mechanisms to their surroundings. In case you want to learn more about this research, Dr. Hoch did a write up last year fr the Deep Sea News site, and his work has also been highlighted on the NewScientist. J. Matthew Hoch (2010). Effects of crowding and wave exposure on penis morphology of the acorn barnacle, Semibalanus balanoides Marine Biology, 157, 2783-2789 : 10.1007/s00227-010-1536-z
Saw this cool Stickleback music video. Check it out.
Btw, this video actually got me to thinking of a poster I saw at the New York Marine Sciences Consortium. It was presented by Peter Park of the Department of Ecology and Evolution at Stony Brook University. He works in Michael Bell’s lab. A main focus of that research is the evolution of brain and learning in sticklebacks. It was pretty interesting stuff, although at this point, its beyond my full comprehension. Check out their lab site to learn more about the work.
In the most recent issue of Marine Biology, there is a manuscript addressing the issue of 2 introduced species and their interactions with one another. Its an interesting read – one of the species is a commercially important bivalve, the Manila clam, which was introduced in the early 20th century and is now one of the most commercially harvested clams on the west coast of the US. The second is Zostera japonica, dwarf eelgrass, an introduced seagrass species which can establish itself on tidal flats. The idea is that this new seagrass species may be of detriment to the now commercially important manila clam. While there is certainly literature which suggests that seagrasses might enhance bivalve growth – see works involving hard clams and eelgrass by Elizabeth Irlandi and Mike Judge – it certainly stands to reason that eelgrass dampens water currents, and likely decreases the amount of food available to suspension feeders, particularly those distant from the edge of the seagrass (where the food availability might be enhanced). And so the team led by Chaochung Tsai aimed to investigate the impacts the invasive eelgrass had on the clams, and whether the clams might enhance the introduced grass. They chose 3 habitats – seagrass present, seagrass removed, and harrowed habitats. The presence of seagrass, while not necessarily impacting shell extension of the infaunal manila clam, did significantly negatively influence clam condition (tissue weight to shell volume ratio). On the flip side of the coin, while bivalves have been shown to influence eelgrass growth through nutrient additions – see the Peterson Lab publications – this apparently is not the case for the manila clams and dwarf eelgrass. In this experiment, clams did not enhance growth nor impact sediment porewater nutrients. In fact, the only positive effect of the introduced seagrass was on itself. Pretty interesting (and before I read it, unexpected) results.
Tsai, C., Yang, S., Trimble, A., & Ruesink, J. (2010). Interactions between two introduced species: Zostera japonica (dwarf eelgrass) facilitates itself and reduces condition of Ruditapes philippinarum (Manila clam) on intertidal flats Marine Biology, 157 (9), 1929-1936 DOI: 10.1007/s00227-010-1462-0 Irlandi, E., & Peterson, C. (1991). Modification of animal habitat by large plants: mechanisms by which seagrasses influence clam growth Oecologia, 87 (3), 307-318 DOI: 10.1007/BF00634584
Judge M, Coen L, Heck KL (1993). Does Mercenaria mercenaria encounter elevated food levels in seagrass beds? Results from a novel technique to collect suspended food resources Marine Ecology Progress Series, 92, 141-150
I am a marine biologist that is currently attending graduate school at the School of Marine and Atmospheric Sciences, Marine Sciences Research Center, of Stony Brook University, New York. I am very interested in marine ecology and have been focusing my studies on bay scallop interactions with their habitats. I plan to investigate various anthropogenic impacts on bay scallop populations for my PhD dissertation. This blog will highlight the details of my graduate research, from bay scallop-eelgrass interactions as previously mentioned, to alternative habitats for scallops, such as Codium, to trophic cascades, and more. Enjoy!
Is a useful experimental tool to mimic natural seagrass while controlling many factors, such as density, canopy height, leaf number, which are usually confounding in natural eelgrass meadows.
Scallops seem to love this stuff!