Last week I was able to get down to Key Largo for the American Water Resources Association (AWRA) Florida chapter annual meeting. Like any opportunistic biologist I always take the opportunity to look around.
The first place I went before even checking into my hotel room was John Pennekamp Coral Reef State Park. One of my favorite things to do there is to snorkel around mangrove roots. People familiar with mangroves often know that they harbor a complex root system (especially red mangroves with buttressing roots) that protects and supports many species including juvenile fish. What surprised me on my first visit several years ago to the park, is how many different things live on the roots themselves. These epiphytes (“epi” meaning on, and “phyte” meaning plant) and epizoans (“zoans” refers to animals) are vibrant and diverse. The delicate little tendrils of minute anenomes are littered in among examples of solitary and colonial species of tunicates, little squishy organisms with in-current and ex-current siphons. Clusters of Isognomon alatus, the flat tree oyster, are visible. It’s an amazing brackish little universe.
While they may seem a little frenetic, I captured a couple videos as well. The first is a little tour of the mangrove roots I describe above:
And the next is of a small barracuda I followed for a moment or two:
I later moved my prospecting off shore a couple days later when I donned scuba gear with Rainbow Reef Dive Center. Besides the surprise siting of an interesting shark or notable sea creature, one of the appeals of diving down in the keys is the intricate landscape of benthic creatures including things like corals, sponges, and christmas tree worms.
And while I can always be kept busy watching the variety of oddly colored and shaped fish, the appearance of a rather large green moray eel doesn’t disappoint!:
Thanks in part to the generosity of donors to my crowdfunding campaign, I’ve started the process of listening to fishermen and oystermen in St. Augustine and nearby!
In order to capture different ideas and access multiple types of people, I am using a technique commonly called snowball sampling. Every time I interview someone, either formally or informally, I ask them who else I should be talking to. The idea is that eventually there will be enough overlap in the answers you’re getting that you know you are starting to capture the population you’re interested in. This approach is known to have some drawbacks in that it can be challenging to not talk exclusively to people who think similarly to one another. However, when your target populations are small, this method may be the most effective way of accessing them.
While not giving too much away, I’ll also say that I’m already noticing some common themes in the answers I’m hearing to my questions which is exciting. I’m learning interesting details about what fishermen and oystermen look for in reefs. One of the most enjoyable aspects however, is the extra details that are being shared, the personal history and anecdotes people are peppering in with their responses. The experience of local oyster roasts has been mentioned, with each telling rich in explanation about methods of cooking and cultural significance. Stories about growing up on the local waterways abound as well. This kind of research is affording me a chance to really root around and understand the complexity of ways these groups are identifying with this resource, and I’m excited to have the opportunity.
Keep an eye on my blog for continued updates on all things oyster!
Full disclosure, I was once not the oyster devotee I am now. As a proper native New Englander and marine biologist, I of course was acquainted with them. But it wasn’t until I trekked across the eastern coast of the United States and wound my way down to start a PhD program at the University of Florida with molluscan biologist Shirley Baker, that I began to suspect there was something more salient about my study organism.
In the great assemblage of all the graduate students that ever were, many a person has chosen a dissertation topic out of convenience and as a means to an end. Things may have started out in a similar vein for my own research. Currently it seems oysters are a sexy topic, and ecosystem services – the benefits of nature that directly influence human wellbeing, an even sexier one. But as I began to work on my research I began to realize the uniqueness and gravity of Crassostrea virginica, the American Oyster.
Like most people with a glancing familiarity with oysters, I knew they were filter feeders, making them unknowing proponents of positive water quality in many an estuarine region. Under this premise, I started field research at the Guana Tolomato Matanzas National Estuarine Research Reserve (which we call the GTM NERR for brevity’s sake) in the St. Augustine region of Florida to examine clearance rates of oysters within the system. So far I’m learning interesting lessons that I continue to explore. While the Nature Conservancy posts the following graphic about the filtration capacity of a single oyster, I’d like to provide the caveat that this indicates what an oyster could do, not necessarily what it does do:
Within the reserve, oyster clearance rates are often lower than lab studies might estimate. But this can often be attributed to the complexities of the natural environment and their influence on the biological processes of organisms. Oysters feeding rates can be influenced by qualities like temperature, salinity, and the nature of the particles in the water they are feeding on. Within the GTM NERR, we’ve also found evidence that tidal cycles may be hugely influential in how much time certain parts of reefs have available to feed.
But while I continue to reveal information on oyster filter feeding within the reserve, I had less initial insight about the full worth of the expansive reefs I was seeing. I did not know how much of a refuge oysters provide until I started to find the squidgy, pinchy little creatures while working on reefs. If you grab a cluster of oysters and rotate it in your hand, you’ll see the craggy irregular patches of barnacles interspersed with often minuscule ribbed mussels hanging on dearly by their byssal threads. Porcelain crabs will flatten themselves against shell in a desperate effort to avoid detection. While collecting oysters, you may also spot sea cucumbers and oyster toadfish while sheepshead and blue crab loiter nearby.
I also didn’t fully appreciate the bastion of strength reefs are against the storms that regularly visit Florida coastlines. It’s suggested oyster reefs have the ability to pace themselves with sea level rise, making them a common and ideal constituent of living shoreline designs which are meant to function as hardier and more effective alternatives to grey infrastructure historically used for shoreline armoring.
The title of my post then refers to the measure of what oysters can teach us about the sometimes unexpected ways we are tied to our environment. But if we attune ourselves to what oysters have to say about the health of our coastlines, we should also listen to one another about the values and concerns we imbue these natural resources with.
In St. Augustine, oysters also provide a source of harvest both directly for oystermen and for fishermen who recognize reefs’ ability to foster good fishing grounds. However, ability to access reefs and to harvest oysters depends on regulation especially in relation to water quality; oysters need to be gathered in locations where they are deemed safe enough to eat. Resource managers are often trying to balance providing positive harvest experiences with optimizing the other services oysters provide.
Information on how fishermen and oystermen currently use reefs, how they would like to use reefs, and how things have changed can then be crucial for the decision making process around managing oysters. We can try and gather those details indirectly or we can talk to these groups directly – a route I am currently tapping into. Through one-on-one interviews, people are telling their stories, revealing vital information about oyster use in the area, and teaching me about the fascinating culture and relevance of oysters within their coastal experiences. I hope study results will lead to more targeted management recommendations and provide opportunities for public outreach, education, and local engagement. Simultaneously, I am quickly learning to embrace my burgeoning love for human dimensions and social science research. All because of oysters. Who would have thought?
If this research interests you, especially my current study on the perception around and use of oyster reefs by oystermen and fishermen, consider donating to my crowdfunding campaign. My friend Natelle, of Natelle Draws Stuff, has designed these amazing postcards and stickers for those who would like some oyster swag:
Yet again drones have proved an invaluable instrument for new discoveries, especially when it comes to observing marine mammal behavior (see my past post: Whale Tales – Current Cetacean Communiqués). The subject in question this time is the strange and elusive Narwhal.
The edited footage above conveniently highlights moments where individual narwhals stun passing cod with a solid tap of their tusk. It’s an interesting hunting method, but one that is rivaled by other examples in the marine world. Many species immobilize their prey; some, like sailfish, use similar techniques, while others may use contrasting tools. Electric Rays and eels shock their quarry, while pistol shrimp usehigh-speed cavitation bubblesto daze their targets. Archer fish knock their dinner out of overlying branches by spitting a stream of water at them.
The purpose of the narwhal’s tusk likely doesn’t stop at clubbing unwitting prey. The absence of an enamel coating on their tusk supports the idea that these animals might be using them in a sensory capacity, allowing the specialized tooth to come into contact with surrounding water masses to detect environmental changes such as salinity and temperature, as well as chemical cues in the water associated with food and mates. Pairing this awareness of their surroundings with highly directional echolocation also allows them to find sometime slim openings in Arctic ice coverage where they can surface and breath as needed.
However, these animals may still suffer catastrophic events living in the extremes they do. Pods of narwhals occasionally suffer entrapments when rapidly shifting weather conditions cause unexpected freezing over potential air holes leading to open water. Kristin Laidre, a researcher at University of Washington’s Polar Science Center, noticed the frequency and timing of those events may be changing with recent shifts in Arctic climate. This, paired with a variety of additional stressors to the whales’ habitat, is the focus of one her current research projects examining the behavioral ecology of narwhals in a changing Arctic. She and other researchers have tagged the animals on multiple occasions in Canada’s Baffin Bay to track their movement, the depth of their dives, and associated water temperatures. As it turns out the temperature data has proved useful to other scientists interested in climatology data. Laidre is soon hoping to once again utilize the oceanographic power of narwhals, this time in Greenland.
A new species of Bonnethead has been described in Belize by FIU researcher Demian Chapman, thus the scenario of a single widespread species in that region now becomes the story of one or more species with overlapping ranges. The discovery was made after analyzing a snippet of the shark’s genome.
DNA analysis has allowed a much more nuanced perspective on species-level differences beyond the physical characteristics that were once the focus of classically-trained taxonomists. Now scientists are able to classify variance on a genetic level and have refined the technique. Now researchers use a method called DNA barcoding, which needs to examine just a small portion of an animal’s genomic sequence, and is often compared to scanning groceries at your supermarket’s checkout line. Large-scale efforts to catalog and archive these genetic identifiers, such as Barcode of Life, make this data widely accessible.
In addition, this finding was part of a larger initiative, called Finprint, focused on filling in data gaps concerning sharks, fins, and rays – all of which constitute a group of cartilaginous fish known as elasmobranchs. Finprint uses baited remote underwater video (BRUV) as one of their primary tools for studying these creatures. Much of their work appears to be focused on their spatial distribution, identifying regions that could lead to conflict with other uses such as fishing or areas that can be marked as candidates for protection.
I study oystery things. In my little myopic scientific snowglobe, I know a few things about shellfish, and I know a few more things about oysters. Then I know the most things about oyster filtration. So there’s still plenty of room for surprise.
This very thing happened this year during a local American Fisheries Society (AFS) meeting where I heard a talk about freshwater mussels. Probably because I always seem to be mucking about in briny water rather than its fresher counterpart, I was rather taken aback learning that many of these species have parasitic larval stages.
After females collect sperm that males eject externally, they fertilize their eggs and stow them in their gills where they develop into a minuscule larval stage called glochidia. These juvenile mussels cannot fully develop however until they somehow reach a host fish. They will encyst themselves into the host’s tissue where they will stay until more fully formed, at which point they will drop off and settle on the river floor. The host fish has graciously and perhaps unknowingly provided the small creature with protection and dispersal.
The strangest detail of this whole process seems to be the intricate tactics mussels have developed to get their little parasitic spawn into hosts. Some species concentrate their glochidia into structures called conglutinates that they then release into the water. Many resemble prey items attractive to fish like in the video and picture below:
Others, like mamas in the Lampsilis family keep their little ones closer to them while dangling parts of their mantle tissue to the same affect at the conglutinates described above.
As with other symbiotic relationships within nature, freshwater mussels are incredibly dependent on the health of their host and the system around them. This has further increased the need for continued research and conservation, and in some instances agencies and institutions have fostered cultivation and propagation efforts.
Several news outlets this week have justifiably made a big deal about the Greenland Shark. Recent research suggests these lumbering giants are now the record holder for the longest lived vertebrates we are aware of. This knocks the Bowhead whale from first place, whose age-determination story is fascinating in its own right, bolstered by the presence of an antique eskimo harpoon point.
Often sharks have been aged through examining growth bands present in vertebrae, however Greenland sharks have softer vertebrae that make this challenging. Additionally, due to challenges in reading these rings as sharks age, as well as possible disconnects between growth rate and age, radiocarbon dating has been joining the toolbox for determining fish longevity. This study used the method with the sharks’ eye lenses.
These sharks may take up to 150 years to reach sexual maturity, making their population vulnerable if too many individuals are culled before reproducing. They are also bizarrely prone to parasitism by a strangely-elongate copepod (most look more shrimp or lobster-like) that attaches to their eyeball and ultimately causes a march towards blindness. Only 1% of the 1500 sharks in a study concerning infection rates were parasite-free. 85% are afflicted in both eyes. However, due to their reliance on a keen sense of smell, rather than sight, for hunting, it has been suggested that the sharks may actually benefit from the copepod acting as small visible lures that interest nearby prey. However, Dr. George Benz of Middle Tennessee State University with expertise in shark and ray parasites, doubts this theory, instead favoring the idea that Greenland sharks may instead be ambush hunters, taking their targets instead through the element of surprise.