Episode 6: Blue Carbon Where the Stingray Meets the Horse Conch
At the beginning of September, Randall and David had a visit from Dr. Peter Macreadie of the University of Technology, Sydney. In this video, Randall takes Dr. Macreadie for a snorkel in St. Joseph Bay.
Dr. Randall Hughes FSU Coastal & Marine Lab
We now focus our attention to seagrasses, which as it turns out, often don’t get a lot of attention, at least in comparison to other marine habitats like coral reefs or even salt marshes.
Randall snorkels in a seagrass bed in Saint Joseph Bay Peninsula State Park. Photo by Dr. Peter Macreadie. Peter is a researcher from the University of Technology, Sydney, who is visiting Randall and David.
In part, this lack of attention is due to the fact that seagrasses typically live completely underwater, except at very low tide, and so they are not as noticeable as marshes are. In addition, seagrasses often occur in shallow estuaries not known for their great visibility (and thus not as ideal a location as coral reefs for snorkelers or scuba divers). And, although I disagree, some people just don’t find them very pretty.
Last week as I was starting to think about this post, there was a small uptick in the number of media articles related to seagrasses, at least in Australia. The increased interest was in response to a proposal by the Environment Minister, Tony Burke, to require greater seagrass protection from mining and development projects (read more in this article from the Brisbane Times). As justification for the increased financial burden on companies, Mr. Burke cited the many benefits that seagrasses provide. And just what are those?
Seagrasses (like salt marshes and oyster reefs) provide habitat for many, many fishes and invertebrates. Studies have found that the number of animals living in seagrasses beds can be an order of magnitude higher than the number living in adjacent coastal habitats. Many of these animals rely on the seagrass beds as a “nursery” that protects them from predators until they grow larger. And lots are recreationally and commercially important species that we like to eat. (Scallops, anyone?)
Seagrasses are also incredibly productive plants, sometimes growing more than 1cm per day, and rivaling our most productive crop species like corn. Because a significant portion of this plant material (particularly the roots and rhizomes below ground) stays in place once the plants die, seagrasses can also serve as important ‘carbon sinks’, or buried reservoirs of carbon. In fact, a recent study estimates that the carbon stored in the sediments of seagrass beds is on par with that stored in the sediments of forests on land!
Although lots of the productivity of seagrass beds makes its way underground, some of it does get eaten. Major consumers of seagrasses include urchins and fishes, as well as the more charismatic dugongs, manatees, and sea turtles.
Seagrasses (like salt marshes) also play an important role in reducing nutrients that run off from land into the water. Unfortunately, these nutrients can also lead to the loss of seagrasses, by promoting increased growth of algal “epiphytes” that grow on the blades of the seagrasses themselves. When there are not enough small fishes and invertebrates around to eat these algae, they can overgrow and outcompete the seagrass, leading to its decline. And when the seagrasses become less abundant, the animals that rely on them are also often in danger.
The Big Bend and Panhandle of Florida are home to expansive seagrass beds that also often go unnoticed. But they contribute to the productivity, diversity, and beauty of this area in many ways, as anyone who has been scalloping recently has surely realized!
Here is a quick guide to the animals featured in the video above:
0:40 Horse conch and sea urchin joined suddenly by a stingray
1:41 Juvenile pinfish
1:18 Two shots of a bay scallop
1:33 Sea urchin
1:49 Pen shell clam covered in sea stars (2 shots)
1:56 Horse conch
In the Grass, On the Reef is funded by a grant from the National Science Foundation.
Much like David finds it hard to distill why the oysters that he studies are so intriguing, I often struggle to convey the charisma of the salt marshes and seagrass beds where I spend so much of my time. At least people like to eat oysters! It can be harder for people to find a connection with the plants that form so many of the critical habitats along our coast (unless of course people misunderstand the meaning of “In the Grass” and think I study a VERY different type of plant!). But even if it is not recognized, there is a connection between the salt marsh and our everyday lives. Like oyster reefs, salt marshes provide many benefits to society, particularly along the coast:
1. A place to live (for marine and terrestrial animals)
Periwinkle snails are among the many animals that make use of the salt marsh habitat.
Even if you’re one of those folks who find it hard to get excited about a bunch of plants, don’t tune out – the salt marsh is teeming with animals! Snails, fiddler crabs, mussels, grasshoppers, dragonflies, and snakes (!) are all critters that we encounter regularly when the tide is out. And there’s always a bit of an adrenaline rush when you see an alligator hauled out nearby. Even better, when the tide comes in, there are lots of animals that you and I (or at least, I) like to eat. Think blue crabs, mullet, and sea trout, for starters. Studies in Florida estimate that marshes provide up to nearly $7000 per acre for recreational fishing alone. Not bad.
2. A safer place to live (for people)
Although it’s generally frowned upon to build houses in the marsh (since it makes it hard for all those animals I just mentioned to live there), it’s a great idea to have lots of healthy marshes near your coastal property. Marshes can protect the coastline from waves and storms, leading to less damage in areas with marshes present. One estimate places the dollar value of coastal protection in the U.S. at over $8000 per hectare per year in reduced hurricane damages! Although here’s hoping that we don’t get an opportunity to test that particular benefit this year.
In addition to reducing the size and strength of waves, marshes also prevent coastal erosion. An unfortunate example of the role of marshes in erosion control came following the Deepwater Horizon oil spill – plants in areas of the marsh that were heavily oiled died, leading to greatly increased rates of erosion in those areas (Silliman et al. 2012). Although the benefit of marshes for reducing erosion and combating sea level rise has been recognized for a long time, there are not any good estimates for what this erosion control is worth in $$. Given expectations of sea level rise in the coming years, I think that the motivation to understand the conditions that lead to sediment accumulation in marshes will only get stronger.
3. Clean water (for animals and people)
Because marshes lie at the intersection of the land and the sea, they serve as a filter for things trying to move between the two. When it comes to run-off and pollution from the land, it’s a very good thing that they do. Simply having a marsh present can serve as an effective alternative to traditional waste treatment. Of course, the protection can go the other direction too – marshes played a critical role in keeping oil from the Deepwater Horizon oil spill from getting to higher elevations.
4. A place to graze (for livestock)
Support for livestock grazing is an important role of marshes in some areas, including the U.K. Although it’s not a benefit commonly associated with marshes in this area, the decaying fence posts that extend out into some areas of St. Joe Bay suggest that it wasn’t too long ago that marshes were used for a similar purpose here!
I could go on, but these and other benefits of marshes are described in greater detail in a recent review by Barbier and colleagues (which I referenced on this blog in May of 2011). Here is the table that they put together summarizing the monetary benefits that we derive from intact salt marshes:
Luckily for us, salt marshes keep working their magic even in the absence of accolades or appreciation. But greater appreciation is needed to help curb the decline of salt marshes around the world – estimated to be as much as 2% per year! We hope that this blog will help generate greater understanding and enthusiasm for the incredible coastal habitats that we are lucky enough to work in every day. Let us know how we’re doing!
In the next two weeks, we delve into a habitat that we have only occasionally covered: seagrass beds. Next week we examine, with visiting researcher Dr. Peter MacReadie, seagrass beds’ role in fighting global climate change. The week after that, we head to Bay Mouth Bar, one of the most ecologically unique places in the world. Also, we’ll be look at the failure of the Apachicola Bay oyster reefs from a biological perspective. Here are a few images of our visit to a Saint Joseph Bay seagrass bed and of Bay Mouth Bar at low tide, when you see all kinds of strange and interesting creatures:
In the Grass, On the Reef is funded by a grant from the National Science Foundation.
Weeks ago, we came up with a schedule for posts and videos and somehow had our video on oysters due for the week after Governor Scott declared this year’s oyster harvest a failure. This led to one minor alteration in the above video, but the video was meant as an overview to the services provided by oyster reefs. There will be content related specifically to Apalachicola Bay in the coming weeks.
Dr. David KimbroFSU Coastal & Marine Lab
There are a lot of things that a marine scientist can study such as charismatic animals (dolphin and turtles) or the waves and currents that fuel my surfing addiction. So, why do I spend most of my time mucking around in mud to study the uncharismatic oyster?
Short answer: because they can provide the foundation for a lot of things that we depend on. Now, some of these benefits or services are obvious and many others aren’t.
Let’s start with the obvious. Just like raising cattle supports tons of jobs and our appetite for hamburgers (I recommend reading Omnivores Dilemma if you want to see how eating meat can be environmentally friendly), the harvesting of oysters financially supports many folks as well as the scrumptious past time of tasting oysters on the half shell as the above video just showed me doing at my local favorite, the Indian Pass Raw Bar!
Unfortunately, the importance of this service was made all to clear to us when the Florida governor recently declared this year’s harvest to be a failure and applied for federal relief for the local economy (Download a PDF of the Department of Agriculture and Consumer Services report here). It’s also unfortunate that this type of bad news has a history of indicating that this natural resource is in trouble and that more trouble may be on the way. To see why, check out a study by Dr. Michael Kirby that showed how this service progressively collapsed from New England down to Florida over the past three centuries. In a nutshell, the pattern of collapse mirrors the increasing number of humans that have over-used this service.
But even if there are no questions about the importance and collapse of the previous service, many folks are asking great questions about whether oysters provide other important services in the form of protected reefs that may offset or exceed their commercial/restaurant value. In other words, what good are oysters to us if they don’t make their way to the raw bar?
An oyster reef built by Dr. Jon Grabowski and Dr. Randall Hughes in 1997, pictured in 2002.
Well, my good buddy Dr. Grabowski’s research used relatively tiny oyster reefs to highlight one less obvious service that involves reefs really ramping up the numbers of commercially and recreationally important fishes (drum) and crabs (stone crabs and blue crabs)….yum! Given that the oyster reefs used to be 12 feet tall and as long as football fields, can you imagine how many crabs and fishes hung around those really big reefs way back then? Heck, even I could have caught a fish!
Another thing that charismatic and good tasting animals need in order to keep our eyes and tummies happy is some healthy coastal water. Having too much plant-like material (phytoplankton) floating around in the water, sinking to the bottom, and decaying can deplete all of the water’s oxygen. Because such a place is very uninviting for lots of sea life, low oxygen areas will not have many animals that are pleasing to the eye, the fishing rod, or our palette.
While it’s hard to know if today’s tiny amount of oysters reefs sufficiently filter enough water, we do know that the really big reefs of our grandparents and their grandparents time were essentially like huge skimmers in swimming pools as big as the Chesapeake Bay.
As the ESPN football talking heads like to say: C’mon Man! Really?
I kid you not, because Jeremy Jackson and colleagues dug through some Chesapeake mud to figure this out for us. Preserved in the mud is stuff that settled out from the water over time, with deeper mud containing older stuff and shallower mud containing newer stuff. It turns out that as we over-ate and turned the larger oyster reefs into small ones, the stuff in the mud transitioned from sings of healthy water to symptoms of unhealthy water. And because the oyster crashes came before the drop in water quality, it’s more likely that oysters maintained the good water signs as opposed to the reverse scenario of the good water signs maintaining the big oyster reefs.
So this points to a third type of service that oyster reefs CAN provide in the form of water-quality. Admittedly, it’s hard to put a dollar amount on that as opposed to the dollar amount that a dozen raw oysters brings in at a raw bar.
But another less obvious way that oysters can help maintain water quality is by removing the nutrients that a lot of the unwanted phytoplankton depend on.
Slide by Ashley R. Smyth, Piehler Lab, UNC Chapel Hill Institute of Marine Sciences.
You see, after oysters suck in the water, filter out their preferred phytoplankton (some are good, but some probably taste as bad as my poor attempt of making southern biscuits), they eventually “poop” their waste out into the mud. Some of this waste makes all sorts of bacteria do all sorts of different things. One of these cool things involves taking a form of nitrogen (think fertilizer on your lawn) that is readily sucked up by nasty phytoplankton and converting it into a form that phytoplankton can’t use (think bad fertilizer that you want to return for a refund). This is called de-nitrification, and it’s a way that oyster feeding and pooping can help maintain healthy coastal conditions. Even cooler, we can slap a dollar amount on it if we think about how much money it costs a waster-water treatment facility to remove the same amount of nitrogen. My buddy in North Carolina Dr. Mike Piehler did just a study and found that the value of this service is about 2,718.00 dollars per acre of oyster reef. And unlike a dozen raw oysters, this service keeps on giving like the energizer bunny.
Finally, and we are now at service 4 in case you are counting, oyster reefs can buffer the waves and storms that eat away at our shorelines, coastal roads, and homes.
Before signing off, I have to also acknowledge that not every oyster reef performs each of these services. Just like my brother and I look pretty darn similar to someone outside of my family, when you look closer, we are really different. Individual oyster reefs are the same way. Heck, while I can do different things well if you catch me in the morning with a cup of coffee, I often really stink at those same things if you check in with me after a too big and sleep-inducing lunch!
This point segues nicely into my research interest about the “context-dependency” of the obvious and not so obvious services that coastal habitats can provide. In other words, why are some reefs doing some services but others are not? This question really crystallizes the essence of a collaborative project that I’m working on with colleagues from FSU, Northeastern University, University of North Carolina, and University of Georgia.
In our crazy-fun, at times maddening, and democratic research team, we are testing whether the answer depends on differences in big hungry and scary predators like drum and crabs lurking around the reefs. Sure, some of these might eat an oyster that doesn’t make it on to my plate at the raw bar. But overall, they may benefit some reefs by eating a lot of the smaller crabs that really like to munch on oysters. And even if they don’t eat all of these oyster munchers, we’re thinking that their presence may sufficiently freak out oyster munchers so that they spend more time watching their backs and less time munching. Hence, the ecology of fear!
Thanks for wading through this long post. If I promise to write shorter posts in the future, then I hope you’ll follow our journey of testing whether predators help maintain services not only in oyster reefs, but also in the marshes and mudflats of the southeast Atlantic and Gulf coastlines.
In the Grass, On the Reef is funded by a grant from the National Science Foundation
If you’re an oyster lover, this photo might concern you. This was taken yesterday on a long paddle along the Apalachicola River. Participants in this year’s Rivertrek fundraiser (click here for the website) were taking an eighteen mile warm up paddle in preparation for the five day adventure this October. Then, we’ll be tackling the entirety of the River. I snapped this photo about an hour after our lunch break, during the long part of our trip where I learned why stretching before paddling is so important. I was looking for a shot like this one, knowing before I left Tallahassee that morning that those shots would be there. I was looking for a shot like this because it’s a large part of why I’m involved in Rivertrek.
For us, on this blog, it’s a matter of salinity. According to the National Oceanic and Atmospheric Administration, the average salinity of the ocean is 35 parts per thousand (ppt). That’s 35 grams of salt dissolved in every thousand grams of water. Oysters, like those in the famous Apalachicola Bay, can survive within a wide range of 5 ppt to 40 ppt. Yet they thrive predominantly in fresher water. Why is that? It has to do with the organisms that affect the health of an oyster. Oyster drills and stone crabs, both oyster consumers, cannot survive in less than 15 ppt salinity. The oyster disease Dermo (Perkinsus marinus) thrives in 21-25 ppt. That’s why successful reefs are typically found where a fresh water source meets the ocean, like where the Apalachicola River flows into Apalachicola Bay. It’s also why that photo can be of concern: it marks the decrease in fresh water flowing along the Apalachicola and into the Bay (the line marks where water flow had been). That decrease in flow has been a result of drought, but it serves as a reminder of the greater threat facing the River basin: the impending rerouting of water from Lake Lanier, upstream of the River in Georgia, to provide water for Georgia cities.
Houseboats and fishing/ hunting shacks were scattered along the river. The sign on this one identified it as "The Redneck Yacht."
This year will be the fourth year that the Rivertrek fundraiser will benefit the Apalachicola Riverkeeper, who fight to keep water flowing at levels that benefit the dependent industries in the Bay and one of the most biodiverse areas in the United States. This year, In the Grass, On the Reef will be along to provide daily snapshots of the journey. From October 10 to October 14, we’ll have images of the trip and stories of each day’s trek. Yesterday’s tuneup allowed me to experiment with how I wanted to shoot from a kayak using our waterproof cameras. The image looks best when I get closer; the trick is not hitting the subject of my shot, whether it’s a cypress tree or another kayaker. I also saw how best I could arrange my gear so that I could get my work done while paddling comfortably. And I also got to know some of my fellow Trekkers.
I had already known Georgia Ackerman and Rick Zelznak, owners of the Wilderness Way. I will disclose that The Wilderness Way has been a WFSU underwriter, and had provided kayaks to the In the Grass, On the Reef project early on (Riverkeeper has also underwritten WFSU). They provided us our kayaks yesterday as well, and will provide some for the Rivertrek paddle (including mine). Georgia, ever passionate about our water ways, picked up trash along the river and ended up taking a fish hook to her finger. Luckily, we were paddling with an ER nurse.
Eddie Lueken will be one of our crucial support crew during the trek, driving back and forth to bring us supplies and food. One night, she’ll be making us machaca, a tasty sounding Mexican beef dish (with an accompanying bean dish for the vegetarian paddlers). An Emergency Room nurse with a knack for story telling, she had us in stitches (no pun intended) with some of her stories.
Paddling together in a tandem kayak were Jennifer Portman and Chris Robertson. Jennifer is the other media member taking part in the Trek; she writes for the Tallahassee Democrat. Chris will be one of the fundraisers- everyone on the trip except Jennifer and I have to get pledges. He came with several detailed laminated maps of the river. They were formidable in their tandem, often well ahead of us and scouting for the entrance to Owl Creek, where we ended our trip. They, Eddie, Georgia, and Rick were great people to paddle with. The River and its struggles are always a big story in our area, and I’m happy to document a part of that story. The opportunity to get footage along all the different parts of the River is priceless. The River basin has to be considered the ecological epicenter of this area.
L to R: Georgia Ackerman, Eddie Lueken, Rick Zelznak, Chris Robertson, and Jennifer Portman.
Halfway through yesterday’s paddle, we started smelling salt. The River provides for the Bay, but the Bay gives a little to the River, too. Many of the fish that make use of the oyster reefs and seagrass beds in Apalachicola Bay come up the river. Rick even saw a blue crab swimming at one point, over twenty miles up the River. Next week’s video explores the real value of the oyster reef, and how its influence can be felt beyond our coasts. If you haven’t seen the first in our second series of videos, it sets up the commercial importance of the intertidal ecosystems such as those that found in and around Apalachicola Bay. You can watch it here.
Below is a slideshow of our trip, from the River Styx to Owl Creek:
In the Grass, On the Reef is funded by a grant from the National Science Foundation.