Monday, June 23, 2008

Why I HATE spider crabs!

I know, I know “hate” is a strong word, but I can’t think of a more appropriate way to describe my invertebrate nemesis. Spider crabs may be responsible for more failed eelgrass plantings under my watch than any other cause. OK, maybe not ANY other cause as we did really mess up on the site selection thing in the 90’s, but it’s got to be up there…

Above is a picture of a spider crab (Libinia emarginata) eating one of our transplants at the Sag Harbor test plot site. It isn’t bad enough the we can never seem to get plants to survive in Sag Harbor (I’ll write about this soon), now we have crabs yanking out plants as fast as we can plant them! Maybe this has been the problem all along?

In this case I just happened upon the unsuspecting culprit as he casually munched on one of our shoots like he was eating a celery stick filled with peanut butter. He couldn’t have started more than a minute or two before I got in the water.

In the past we have witnessed spider crabs uprooting and dislodging transplants as they always seem to show up right after we plant. They must be attracted to the good smells coming from the disturbed sediments. In most cases they rip out a few shoots along one edge of the plot and back in amid the shelter of the new patch. I can hardly blame them as there is literally nothing else on the bottom at most of these sites (see my “Oasis Effect” comment).

The typical sign of crab damage is a shoot cut cleanly off at a 10-30% angle. This kind of damage is common and it does not seem to harm the plants too much if the trimming is minimal. Occasionally, we do see more crushing type wounds and these are likely caused by crabs as well.

I must say that it is almost (do I dare say it) cute when the young "decorator" spider crabs cut off SMALL pieces of shoot (thus the use of the term “cute”) to add to the forest on their back like a sniper customizing his ghillie suite to blend in with the surrounding landscape.

This time the damage was clearly catastrophic to the shoot and there was no chance of recovery. After I took a couple shots with the camera I grabbed the crab and decided that he was going to be sacrificed in the name of science to see how much he actually consumed.

Once back in the boat a fatal blow to the carapace allowed me to dig through the goo that is a crabs innards. I was somewhat surprised to find that most, if not all, of the eelgrass sections were still lined up at or near the crabs mouth parts.

Later that day, back at the lab, I photographed what came out of the crab and was surprised to find a small leaf tip. Since the shoot that he was eating when I found him was not missing any tips, this obviously came from another shoot. Through my frustration I had a warm feeling knowing that there was one less multiple offender in Peconic Bay.


So much field work so little time…

The last two weeks have delivered nearly perfect weather for field work and we have definitely taken advantage of it! The tides were also cooperative allowing us to get in and out of the creek at almost any hour. As a result, I have spent more time in the boat and underwater than at my desk. I’m not complaining, just stating a fact.

Over the next couple days I want to report on some of what we did. There is much to report, both good and bad, including monitoring at restoration sites, discovery of a new meadow at Fishers Island and other interesting observations.


Friday, June 6, 2008

Planting Grass on Mars?

On June 5th we got in our first plantings of the “Seepage Project”. At this point we are one site down and two to go… I need to wait for the groundwater crew to better define the other two sites before we can plant them.

This site, on the east side of Jessup’s Neck, appears to be a major upwelling area as indicated by the dark staining of rust red on an otherwise tan sandy bottom. It literally looks like a moonscape with silver bubbles. Even when we dig down into the sand it shows evidence of reduced iron with a strong dark blue color.

It is getting late to transplant in the PE, but I am hoping that the temperature moderation of the groundwater will help to reduce the stress on the plants. The control plots outside the seepage will not have this benefit, if there is any.

Kim and I were able to plant out four 1m2 plots, two in the seepage and two outside of the seepage. Now its time for Brad and his crew to follow plant growth and survival. Since they plan to destructively sample (remove plants over the summer) we also planted a plot for us to follow over the coming months.

As part of this project we also deployed two temperature loggers under half cement blocks on the sediment surface. If there are any differences between the flow and no flow sites, these should pick it up.

While we were planting we witnessed something that we have never seen before, a clam spawning. Check back for a note and pictures describing this event.


The Robins Island Plots Thrive…

In order to track the progress of our various test plantings throughout the region we typically schedule monitoring visits at least monthly throughout the growing season. Sometimes, especially during late summer when we can begin to lose plants to stress, it is useful to monitor more often, if possible.

Last week we made our second monitoring visit to the Robins Island test plots that looked so good in April. If you remember my last post on this site I mentioned that these plots were the best that I have ever seen in over 15 years of work in the Peconic Estuary. However, as they say in the investment commercials “past performance is no guarantee of future results” or some such thing.

Having said this, I could not have been happier with what we observed on May 29th. The day was perfect for monitoring. The sun was shining and there was a slight breeze, not enough to produce a chop in the lee of the island, but just enough to keep the “noseeums” away.

As we approached the plots we could clearly see the dark circles against the tan of the surrounding sand. I was relieved that they were still there. Fortunately or unfortunately, depending on how you want to look at it there is literally nothing on the bottom at this site except for what we planted; No algae, no crabs, no whelks, no anything...just as we like it. In areas like this our plots normally experience the “oasis effect” (I think I just made that up) meaning that any crab, whelk or moonsnail in the area eventually arrives and rips or plows out the grass looking for food. For some reason, this does not happen here.

Given the water clarity I could almost count the shoots from the boat, but that would clearly not be accurate enough for our work. What was apparent from above was that the plots contained many flowers indicating that there will likely be a nice seed set this summer.

In my mind the flowers are a mixed blessing. On one hand they indicate how well the site is performing. On the other hand they also mean that the site will lose shoots after seeds are released some time mid summer.

For those who don’t know a certain number (about 10%) of vegetative shoots typically develop into reproductive shoots, set seed and die. This appears to be initiated some time during the winter or very early spring and no one really knows what causes an otherwise normal shoot to differentiate. What is clear however is that as a result of this process the shoot density after flowering always drops proportional to the amount of flowering.

As usual Steve handled the counting as he has the most skilled and experienced of us. When there are flowers we count them separately so we can account for the eventual loses and we also want to calculate flowering percentage.

Based on the numbers from April to May the plots have shown an 8% drop when the reproductive shoots are included. Mean flowering percentage was 15.8% which will translate into an approximately 30 shoot loss per plot by mid summer. However, we also expect additional lateral shoots to form in the coming weeks so this number COULD be overcome be increases in additional vegetative shoots.

We also checked on the Hog Neck Bay plots on the same day. They looked good, but not as good as Robins Island. Check back for an update on these plots soon.


Wednesday, June 4, 2008

Attack of the Sea Robin!

I know, I know they’re not known for being vicious, but as I found out this week, Sea Robins can be very aggressive. While minding my own business documenting some of our newest test plantings off Little Ram Island (Shelter Island) I was accosted by a male Sea Robin in breading color.

Kim and I were just completing a rock planting in about 8 feet of water and I wanted to document the extent of our work with some “before” pictures to compare to what will hopefully be great “after” pics as the grass spreads. You’ll have to check back to see if this actually happens.

Anyway, while I was busy taking pics, I saw this guy approach pretty close and start to do wide circles around me in and out of the extent of my visibility. Most fish we come across, except for our flounders at St. Thomas, which is another “fish” story, are very wary of us and either dart away as we approach or stay away from us completely.

I have experienced a menhaden (aka Bunker) school close up in the LIS that reminded me of a show on the Discovery or the National Geographic Channel as the metallic school morphed around me as it passed. I have also had stripers circle me as well. However, in both cases if I exhaled the fish instinctively moved away.

This time was different! What I thought would be another quaint encounter with a docile denizen of the deep turned into a case of aggravated assault.

At first I thought this guy was simply there to clean up a couple of the spider crabs that I had sacrificed for the cause. Yes, I must admit that I like to offer up spider crabs to nearby fishes as there are more spider crabs out there than we can shake a stick at…and they like to dig up our plots. The phrase to “kill to birds with one stone” comes to mind but “to kill two crabs with one stone” is right on target. Back to the story; this guy had more on his mind than the free handouts though.

As I innocently went about my business getting some great shots of the plantings apparently he grew tired of me trespassing in HIS territory. That’s when it all changed. As I looked down in the viewer to look at a previous pic he suddenly charged me and spread his wing-like pectoral fins out and almost hit me in the face. I couldn’t believe it!

It took me a second to process what had just happen in the rush of activity, but I realized he meant business as he circled even more vigorously. At that point we were done with our work and I was more than happy to leave this proud male to his own devices as I doggy paddled back to the boat with my tail between my legs. I had to give it to him for sticking up to something that was much larger. And, let’s face it I know when I had been summarily beaten…


Seahorses off Shelter Island!

Call it luck…call it an amazing coincidence, but on the year when we planned to initiate a Seahorse Research project in the Peconic Estuary we found natural seahorses! That’s right, natural seahorses happy and healthy in the PE!

This past January I had met Todd Gardiner from the Atlantis Marine World Aquarium when we gave back-to-back lectures at the Friends of Flax Pond Winter Lecture Series at the Childs Mansion in Old Field. I had never participated in a “tag team” lecture before, but this one was arranged in such a way that I presented the habitat side (eelgrass) and Todd discussed the fisheries (seahorses).

While listening to Todd’s talk I became aware of the plight of local seahorses (Hippocampus erectus) and the fact that their numbers appear to be dropping, even in the Great South Bay where he regularly finds them. He also discussed that there was no current protection for this species and that large numbers are being harvested for the pet trade.

As usual, my mind raced with new project ideas. If we are already planting eelgrass in the PE why not team up with Todd and introduce seahorses as we plant our eelgrass? If this works we could introduce habitat and the animal it supports almost simultaneously. Not really, since there would have to be a delay as the grass becomes established and attracts suitable food for the seahorses, but that is the basic concept.

As a follow up, Ali and I had a meeting with Todd to see how we could coordinate our efforts. It was decided that we would work with Todd as he is THE local expert and he typically has a supply of both hatchery reared and wild caught seahorses on hand at the aquarium during the summer.

This year we planned to introduce a number of seahorses into different sized natural and/or planted plots in the PE to see what size is big enough for these little creatures. For obvious reasons we want to find the smallest size that will still support an adult pair. This way, when we plant this fall we know what sized plots to establish so that the seahorses get what they need.

On May 28th part of our project took a quantum leap forward. While scouting for new planting sites off of Little Ram Island Kim found a very small remnant patch of grass. As she was taking pictures of this dwarf (6”) tall grass she found a pair of seahorses clinging to the base of the plants. As you can imagine she was more that just a little excited.

On the same day a dive at another site with very short grass in shallow water also yielded a number of healthy looking seahorses. Apparently seahorses are alive and well in the Gardiners Bay.

On the following day and early this week we found additional animals, all in small patches of grass east of Shelter Island. In my 15 years of diving in the PE I have NEVER seen a seahorse and now we know exactly where to look for them!

We look forward to following these guys and learning more about them. Hopefully, what we learn this summer will allow us to adapt or eelgrass planting methods to the point where we can introduce seahorses back into the central and western PE at one of more of our planting sites…