Zostera marina is a seagrass species, commonly known as eelgrass, that is found on both coasts of the United States, as well as in Europe. Unfortunately, Zostera is disappearing all over the place, including right here in New York. This could have devastating impacts on animals that rely on eelgrass as foraging grounds, or, as is the case with scallops, use it as a refuge from predation. This is its story, as seen through the eyes of an aspiring graduate student...

Tuesday, May 18, 2010

Here today, gone tomorrow!

A complete and utter failure? You decide. Last fall I had the bright idea to track overwinter survival and subsequent spring conditioning for scallops released in different habitats (eelgrass - their preferred habitat, see Thayer and Stuart 1974; Codium fragile - an introduced macroalgae which we think might serve as a suitable alternate substrate in the absence of eelgrass; and unvegetated, as a baseline for comparison). I have examined these habitats for growth in juvenile scallops and have already published some short term survival data (Carroll et al 2010, see earlier posts for a link). So my bright idea was to free release a fairly large number of scallops into these habitats at two field sites, one in Shinnecock Bay and one near Sag Harbor, NY. This is a method we have used in the restoration efforts, and a method that has been successful, so I figured that it would be no problem. I planted ~2500 scallops in each habitat at the 2 sites (~15,000 total scallops planted), not an insignificant number, at least not in my opinion back in November/December of 2009. In other planting sites, we typically don't monitor again after planting until the spring, so staying true to form, I did not actually go check on these scallops until last week. Much to my surprise (well, maybe not totally surprised) I didn't recover a single scallop in Shinnecock Bay. I surveyed all the habitats around my planting zone and didn't find a single live scallop, save for a couple natural 2 year olds. My dreams of having some uncaged growth and condition data failed! There wasn't even evidence of major predation, because I didn't even find empty or crushed shells. They were just all gone! A couple things are likely - either burial or transport - see Powers and Peterson's 2000 manuscript on scallop movement. Both are equally possible scenarios, as these sites in Shinnecock Bay were relatively shallow (~1m deep) and we had quite a crazy winter in terms of storms. Its just a shame. The only positive here is that at least my marker buoys were still firmly anchored at the sites! In fact, this picture is about the most exciting thing from the Shinnecock dives:

(thats right, its my pink lemonade by the throttle while the boat is tied to the dock. Nice, right?)

I was hoping Sag Harbor would be slightly better. I mean, this was a deeper site, so things had to work out, right? Actually, I originally expected there to be scallops at Shinnecock (typically low energy sites) and not in Sag Harbor (strong tidal currents). In Sag Harbor, the scallops already drifted slightly down current from the planting area the date of planting, and despite the scallops looking good at the bottom,

I figured strong currents and potential predation

would essentially eliminate them. Luckily, there was scallops to be found in Sag Harbor, although in much reduced densities. So, not enough scallops to monitor with enough replication to have confidence in the results, but at least all of the 7500 scallops here were not lost. What was lost, you ask? The Codium! It was all gone! My Codium planting area in Sag Harbor was completely devoid of Codium! So despite the semi-success of overwintering some of the scallops in Sag Harbor, my experiment here still failed! Awesome! I guess there's always NEXT year, I just don't know how my committee feels about that!
I guess this season, I will just have to run juvenile growth experiments again, as soon as I get the juveniles.

At least I saw some cool stuff at Sag Harbor:

Spider crab crawling out from a cinder block.

Red beard sponge in eelgrass.

Surviving bay scallop, cryptically hidden on the bottom, save for its blue eyes!

Juvenile lady crab.

Thayer, GW, & Stuart, HH (1974). The bay scallop makes its bed of seagrass Marine Fisheries Review, 36, 27-30

Powers, SP, & Peterson, CH (2000). Conditional density dependence: The flow trigger to expression of density-dependent emigration in bay scallops Limnology and Oceanography, 45, 727-732

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