Eclectic Echoes

After posting to the Scallop of Hearts to TO95%, I remembered it’s Blog Action Day for the cause of climate change awareness.

One of the major concerns with climate change relates to habitat changes for the plants and animals. Will aspen survive anywhere in the United States? What trees will be able to survive in Connecticut in 2050? 2100? Where will elk be able to survive in 2100?

Of course these aren’t easy predictions to make since each species has distinct environmental requirements. Even more troubling though is that many have complex relationships with other organisms, both beneficial and detrimental. Then there are the often complex food webs that each species is a member. some webs are resilient to loss of several species but others collapse with the loss of only one.

While sea temperatures are generally more stable than air temps in terrestrial systems, many of the marine animals have even tighter requirements for temperature. Even a change in just a few °C can prevent reproduction, reduce lifespans, or even cause death. That is the case with the Icelandic Scallop. In some recent experiments it was found that the scallops had a significantly higher mortality in temperatures above 12°C. Average summer sea surface temperatures off Iceland’s southern coast have been in excess of 10°C in recent years and have been rising. A +2°C change over the previous decades has brought the average summer sea surface temperature very near the scallop’s maximum threshold. While the scallops are still able to survive, there has been a marked increase in adult mortality.

Icelandic Scallop - Image from http://www.osl.gc.ca/guide_sp/en/invert/sp/c-islandica.html

Increasing temperature may not directly be the primary cause of the recent increases in mortality of the scallops, though it has been strongly implicated. In recent years, a protozoan parasite has affected much of the stock of C. islandica around Iceland. As with the scallop itself, many protozoan parasites have been found to have temperature thresholds and ideal temperature ranges. For instance Perkinsus atlanticus populations under controlled experiments did not grow, in temperatures of 5°C, grew slowly at 16°C, and grew quickly at 20°C and 26°C. It also failed to grow and died out after 4 days at an experimental temperature of 37°C. Similarly, two other protozoan parasites of interest on the Atlantic Coast are also temperature controlled: Parkinsus marinus, the cause of the disease dermo in oysters, requires temperatures above 25°C to thrive, Haplosporidium nelsoni, which causes MSX in oysters (although it can survive and multiply at temperatures of 5°C-25°C) requires temperatures above 20°C to infect a new oyster. Temperature is likely also a controlling factor in the spread of the protozoan infecting C. islandica.

While the Iceland Scallop is what instigated this post, the topic of climate change and its effect on marine animals, particularly fish, is one I have been thinking of a lot lately. In much the same way that the scallops are temperature limited, fish have ideal and survivable temperature ranges, and temperature can play a significant role on growth and reproductive success. Complicating the issue is that many of the fish have very specific habitat preferences or needs as well.

Atlantic Wolffish - Photo copyright Peter Auster from http://www.nurc.uconn.edu/bigmouthfishes/photos/SBNMS/content/neg7_large.html

Take for instance the Atlantic Wolffish (Anarhichas lupus) a species of increasing concern in the Gulf of Maine, if fact they are likely to be soon added to the Endangered Species Act. They are a wonderful (dare I say beautiful) fish with some great characteristics and a face only a mother, or a crazy marine biologist, could love! They feed mainly on molluscs, crustaceans and echinoderms using their huge canines. They are a large benthic fish, growing up to 5 feet and weighing up to 40 pounds.

They are also a slow growing and late maturing species. Growth and maturity varies with temperature fluctuations, but generally they are reproductively mature by 6 years or about 16 inches total length. Spawning pairs of male and female form in the spring with actual spawning period varying, possibly as a function of temperature. As with many species, reproductive success increases as females grow larger and older, producing both more eggs and more viable eggs (ranges from 5,000 to 12,000 eggs per season). The female lays her eggs in holes and around boulder reefs. The male then begins a fast, loses his teeth, and guards the eggs for four to nine months of egg incubation (again a function of temperature). Four to nine month fasting and guarding the eggs. Think about that one guys!

wolffish pair from CLF (credit: Jonathan Bird) on Vimeo.

One of the cool things about wolffish is the presence of anti-freeze in their body, which allows them to survive, even thrive, in extremely cold waters. In the wild they have been caught in trawl surveys in waters from -1.9°C to 14°C. In the laboratory they survived temperatures as high as 17°C, but feeding was strongly negatively correlated with the higher temperatures.

So temperature is a major factor on the wolffish, but so is habitat. Wolffish are most often found in rocky reefs or seaweed beds on hard substrate from 80m to 180m depths, but range as deep as 650m and can, on occasion, be found in coastal shallows. My most memorable dive in New England remains being about 3 feet away from a 4 foot wolffish in the cove just off Avery Point in late November.

Young wolffish keep to the deeper, colder part of their range where temperatures remain -1°C to 4°C. Only mature fish are found in shallower ranges and higher temperatures with an upper temperature limit of 10°C.

My thoughts recently have related mainly to mapping the current and potential future ranges of some of these animals using habitat suitability modeling techniques in geographic information systems (GIS), including especially ecological niche factor analysis (ENFA). Using what we know of their habitat requirements (for the wolffish: -1°C-10°C, boulder reefs for spawning, 80m-200m depth, and abundance of lobster, crab, urchin or molluscs) we can map the current optimal and sub-optimal ranges. It doesn’t mean they’ll be there, but it is where the potential for finding them should be highest, based on our understanding of their requirements. By altering the temperature and depth components to match forecasts based on climate change models, we can look ahead to forecast the likely range of the animals, and even the decade by decade march or retreat of suitable habitat.

An example of using mulitple habitat factors with multipliers to determine ecological niche. From http://www2.unil.ch/biomapper/

For some animals the outlook is pretty bleak. The combination of habitat requirements and temperature requirements will drive them completely out of the Gulf of Maine and potentially out of the Western Atlantic entirely. There are many fish that are at their breeding temperature limits in the Gulf of Maine already, including many commercially important species. Some marine animals are existing in virtual islands of suitable habitat formed by complexities of depth, substrate type and complexity, currents and temperature, among many other factors.

The challenge is to identify, for each species or community, which of these factors are most important for both the organism’s survival and our modeling efforts. Unfortunately, especially in the marine realm, there is still so much we don’t know about the ecological requirements of may of the animals and communities. Even mapping the seafloor at resolutions comparable to our maps of terrestrial areas continues to be challenge. It often surprises many people I talk to when they find out that almost all our knowledge of marine animal populations and habitat characteristics comes from commercial fisheries and from sample trawls by the NMFS. Most species that are not targets of fisheries or considered commercially important have not been studied extensively, if at all.

Trawler bringin up it's haul - from http://en.wikivisual.com/images/f/fb/Fish_on_Trawler.jpg

In the marine environment it is very challenging to accurately predict how communities will respond to warming waters and how individual species ranges will change, simply from lack of direct observation. We are getting better at using the important data we do have, and have identified proxies for the data we simply do not have, but we need more time in the water with ROV’s and DSV’s for direct observations, especially of the continental shelf and deep sea ecosystems.

Wolffish eating a sea urchin from CLF (credit: Jonathan Bird) on Vimeo.

References

Burreson, E., & Ford, S. (2004). A review of recent information on the Haplosporidia, with special reference
to Haplosporidium nelsoni (MSX disease) Aquating Living Resources, 17 (4), 499-517 DOI: 10.1051/alr:2004056

Hagen, N., & Mann, K.H. (1992). Functional response of the predators American lobster Homarus americanus (Milne-Edwards) and Atlantic wolffish Anarhichas lupus (L.) to increasing numbers of the green sea urchin Strongylocentrotus droebachiensis (Müller) Journal of Experimental Marine Biology and Ecology, 159 (1), 89-112 DOI: 10.1016/0022-0981(92)90260-H

Jonasson, J., Thorarinsdottir, G., Eiriksson, H., & Marteinsdottir, G. (2004). Temperature tolerance of Iceland scallop, Chlamys islandica (O.F. Muller) under controlled experimental conditions Aquaculture Research, 35 (15), 1405-1414 DOI: 10.1111/j.1365-2109.2004.01159.x

King, M.J., Kao, M.H., Brown, J.A, & Fletcher, G.L. (1989). Lethal freezing temperatures of fish:
limitations to seapen culture in Atlantic Canada. Proc Ann Aquacult Assoc Can., 89 (3), 47-49

Ordás, M., & Figueras, A. (1998). In vitro culture of Perkinsus atlanticus, a parasite of the carpet shell clam Ruditapes decussatus Diseases of Aquatic Organisms, 33, 129-136 DOI: 10.3354/dao033129

One last awesome video of a wolffish!

Wolffish devouring a crab from CLF (credit: Jonathan Bird) on Vimeo.