Benthic Ecology Meetings: Multiple Predator Edition

By JohnnyScallops, on March 20th, 2013%

bemheaderREVISED

I realize that I have not made a blog post in a very long time.  My apologies to any followers I still have left.  Today marks the opening day of the 42nd Annual Benthic Ecology Meeting, and I figured it was as good a time as any to make a new blog post.  Afterall, I have made multiple BEM-related posts in the past, and I am currently waiting for my ride to leave for the meeting.

A lot has changed for me since the last benthic meeting.  I completed my dissertation and relocated to UNCW to start my post-doctoral career.  It has been pretty hectic.  When I first came down, I was trying to finish up some manuscripts from my dissertation, like the chapter on the impacts of Codium fragile on scallop demographics such as growth rate and tissue condition.  My conclusions were that the invasive alga might be beneficial for scallop populations, especially in the absence of their native habitat, seagrass.  I have made this argument before, and this chapter was recently published in Marine Biology.  Other chapters haven’t gone through so smoothly and are still being reviewed, but that is par for the course in this field.

I was balancing those with editing other manuscripts from collaborative efforts with my former lab and one of my committee members.  I also made two failed attempts at doing a laboratory study with oyster spat and an ectoparasitic snail.  The results were promising, but I kept having high mortality across all treatments, and I need to come up with a better way of maintaining and feeding the oysters in a lab setting.  I also have now written 4 proposals to various funding agencies, and am currently working up some old data sets for my current lab.  Within all this, I crammed a 2.5 week trip to Jamaica to attempt to do some sponge work, but the weather didn’t cooperate (well, not with me anyway, my stomach is not the biggest fan of the ocean). Suffice it to say, I have been extremely busy, but that isn’t really an excuse to have stopped making regular updates.  However, I have only been in “the field” once since I relocated, and it’s not very much fun writing blog posts about writing Sea Grant proposals.

However, this will be a nice little break, and I am excited to be headed down to the meeting.  There are a lot of talks this year that promise to be very good and informative, plus there is also the Beneath the Waves Film Festival which is always excellent.  And, in general, I like to see former colleagues, friends, potential future collaborators and have a generally good time drinking beer and talking all things marine science.

My talk this year will involve some work from my former lab on multiple predators.  Natural communities have multiple predators foraging on shared prey resources, and until the last decade or so, these interactions were largely ignored in lab studies.  They are interesting, because the consumption of prey is rarely additive – that is, two predators do not typically consume the same amount of prey you would expect based on how much they can eat when they are alone.  More often, the prey either experiences reduced or enhanced risk relative to expected consumption.  For crabs interactions, which utilize prey and habitats similarly, we expect that antagonistic interactions increase, resulting in reduced risk on the prey.  Check out this video:

Hemi_green

What you can see is the smaller crab is like your annoying little sibling who just won’t leave you alone and constantly antagonizes you.  It kind of makes you stop what you are doing.  In crabs, this means they might stop foraging to deal with each other.  This usually means that the prey survive better than would be expected.  However, this isn’t always the case when you run the trials and do the statistical analysis:

Proportion of ribbed mussels consumed by Hemigrapsus alone (pink bar), by Carcinus alone (green bar) and the two crabs together (gray bar). The circle denotes the expected consumption.

Proportion of ribbed mussels consumed by Hemigrapsus alone (pink bar), by Carcinus alone (green bar) and the two crabs together (gray bar). The circle denotes the expected consumption.

In this case, our observed consumption was not different than we expected, based on individual consumption rates.  We anticipated to see a risk reduction, and based on the video, we know the crabs were interacting.  So what gives? Upon further inspection, when we looked at the sizes of mussels consumed, we saw a dramatic shift:

Pink bars are mussels consumed by Hemigrapsus, Green bays by Carcinus and gray bars by both

Pink bars are mussels consumed by Hemigrapsus, Green bays by Carcinus and gray bars by both

What we saw was that when foraging along, the green crabs consumed all the size ranges that were offered, but when foraging together, they shifted to selecting smaller prey, possibly because they had less time to forage.  So while the overall proportion being consumed stayed the same, they were foraging on a smaller portion of the population.  We thought that was pretty cool!

Stay tuned for more posts, I promise to do better!

Leave a comment   Crabs, Experiments, marine ecology, predation, Research posts

Marine ecology affected by the local weather

By JohnnyScallops, on June 4th, 2010%

ResearchBlogging.orgAs marine scientists, sometimes we forget or don’t even realize how much local baymen and fishermen actually know. Or maybe we don’t trust them because they are “lay” persons. But they work the bay, they try to catch many of the species we study (as money is a big driver of research), and they know things. Local baymen who have worked the bay for years suggest that bay scallop recruitment is higher in years after cold/wet winters. Sometimes, we take what they say with a grain of salt. However, they know. They have often been working with these species for as long or longer than we have, and it is often also a generation thing. Generations of baymen can’t be wrong in their assessment, can they?

A 2001 study in the Dutch Wadden Sea supports these claims, however, their conclusions are not what you think. Matthius Strasser and Carmen-Pia Gunther observed patterns in larval supply of predators and prey after a series of consecutive winters in which temperatures were severe, moderate or mild. Originally, the prevailing thought was that egg production increased after severe winters of many benthos, and this is why recruitment was higher in the following spring. However, their research indicates that the numbers and peaks in recruitment were actually highest in the mild winter. So why isn’t recruitment highest during these years? Their theory, a mismatch in the predator and prey larval supply. After severe winters there is a delay in the peak larval supply of the major predators, green crabs, of almost 6-8 weeks. This delay is not as apparent as their bivalve prey, and with the average larval time of the bivalves also being shorter, they settle much earlier than the green crabs and have a potential head start in growth. According to the researchers, this mismatch is what fuels observations of higher recruitment after severe winters.

An alternative scenario is one which was observed in Chesapeake Bay. Using local climate response variables Kimmel et al were able to demonstrate noticeable and significant differences in phytoplankton, copepod, gelatinous zooplankton and finfish abundances and composition between years with “wet” winters and years with “dry” winters. Essentially, wet winters led to an increase of freshwater flow and nutrients into the system, which resulted in higher phytoplankton, more copepods, more ctenophores and higher numbers of striped bass. In years of dry winters, there was less phytoplankton, more scyphomedusae and more menhaden. The basic premise is that the local climate had a significant impact on the community composition of Chesapeake Bay by controlling the amount of fresh water flux into the system.

Both are interesting reads, and the idea of the interplay between climate and marine ecology is one that is becoming even more important to understand with the current climate change scenarios. It is quite clear that atmospheric conditions and local climate can have a fairly significant impact on subsequent year classes – something baymen have been familiar with for decades, if not centuries, but something marine scientists have only been exploring for the past decade, give or take.

Strasser, M. (2001). Larval supply of predator and prey: temporal mismatch between crabs and bivalves after a severe winter in the Wadden Sea Journal of Sea Research, 46 (1), 57-67 DOI: 10.1016/S1385-1101(01)00063-6

Kimmel, D., Miller, W., Harding, L., Houde, E., & Roman, M. (2009). Estuarine Ecosystem Response Captured Using a Synoptic Climatology Estuaries and Coasts, 32 (3), 403-409 DOI: 10.1007/s12237-009-9147-y

Leave a comment   climate change, marine ecology, predation, recruitment, ResearchBlogging, weather