The south shore of Long Island has a series of interconnected lagoonal estuaries. Shinnecock Bay is the eastern most basin, and it has the least amount of people living along its shores. That’s not to say that there aren’t people out here, it just lacks the uber-development of the more western bays. In recent years, the western portion of Shinnecock Bay has been plagued with brown tides (as has the next bay to the west Quantuck Bay). There was a recent report on NBC News New York on the subject:
The issue is that the brown tides are affecting the Shinnecock Bay shellfish populations negatively. Brown tides were originally responsible for the crash in bay scallop populations over 25 years ago in the Peconic Estuary. Brown tides are a very small phytoplankton that are too small for may shellfish to ingest, and it is also accepted that they produce a sort of toxin that is also harmful to things that eat it, a double-whammy of danger to filter feeders. The problem is these blooms become very dense, essentially outcompeting all other phytoplankton. Since the brown tide becomes the only food available to filter feeders, many either succumb to the toxin or starve to death. This is what happened with scallops in the mid 1980s and 1990s. Luckily, a brown tide hasn’t been seen in the Peconics since 1995 (knock on wood), which led to the restoration efforts I am currently involved with.
However, the brown tide also creates other problems. Some filter feeders, such as clams, appear able to “weather the storm,” so to speak. But brown tides occur at the most inopportune time for hard clams and many other native Long Island invertebrates – spawning season. Clam and other invertebrate larvae are often in the water column at the same time the brown tides appear, and this is extremely harmful to the larvae. A few studies have demonstrated that high concentrations of brown tide can inhibit clam larval growth, extending the larval period and preventing metamorphosis. This has devastating consequences for clam recruitment. Major stressors that occur on basin scales and can severely impact the larvae are likely to lead to recruitment failure (Bricelj and MacQuarrie 2007). In addition, because brown tides inhibit feeding of adult clams, this too can impact reproductive output by affecting gamete formation in adults (Newell et al 2009). This is likely whats been happening in the western portion of Shinnecock Bay highlighted by the above news video.
Brown tides also severely darken the water column. This creates a situation which is harmful to benthic primary producers, such as seagrasses. The brown tide is responsible for shading out eelgrass in a number of Long Island bays (Dennison et al 1989). This has created a loss of a vital habitat for numerous commercially and recreationally important species (which I have blogged about numerous times). This might have been another reason why scallops didn’t recover naturally after the last Peconic brown tide, as eelgrass is often referred to as the preferred scallop habitat. However, hard clams are also known to survive better in seagrass meadows, where the complex root and rhizome structure protects burrowed clams from predators, mostly crabs (Irlandi 1997). Clams also appear to grow better in seagrass habitats (Irlandi 1996, Judge et al 1993).
So now we have a potential triple-whammy for hard clams:
1)Brown tides inhibit feeding in adults, which could impact condition and reproductive output.
2)Brown tides affect the growth of larval clams, preventing metamophosis, and potentially leading to recruitment failure.
3)Brown tides shade out seagrass, causing it to disappear, which has potential negative consequences.
So water quality has deteriorated, and brown tides are becoming an annual occurrence. However, is poor water quality solely to blame? It is also likely that overharvesting of filter feeding shellfish might also play a role in development of brown tide blooms. High densities of hard clams are capable of preventing brown tide bloom formation – densities above current levels but below historic levels, prior to overharvesting (Cerrato et al 2004). It is possible, then, that overharvest of clams (estimated bay wide average for Shinnecock Bay ~1 per square meter) has led to low population densities which are incapable of filtering the water column. This, in addition to water quality issues, allows for the initiation, persistence and recurrence of brown tide blooms, which further prevents hard clam populations from replenishing themselves, a negative feedback loop.
Brown tide in mesocosms with and without clams from Cerrato
This has created some interest in restoring Shinnecock Bay. Both my advisor and one of my committee members are involved in a project investigating the feasibility of restoration, and naturally, I have been tasked to do a lot of work on this project. Before restoration can happen, however, we first need to know the reasons WHY certain shellfish aren’t found in high numbers in Shinnecock Bay. If we are correct in our assumption that recruitment failure due to larval supply is to blame, then we need to investigate recruitment. We are doing this at a series of sites within the Shinnecock Bay-Quantuck Bay complex, and I blogged about this over on the Southampton Patch. If we see many settlers in our collectors, which are generally protected from predators, but we don’t see corresponding numbers on the bottom, we can then correct our theory of recruitment failure to some post-settlement mortality. Once we have this information, we can make better decisions about ways to approach potential restoration projects. And since scallop restoration is working in the Peconics and hard clam restoration appears to be working in Great South Bay, there is reason for hope.
All user groups – baymen, researchers, environmental advocates, recreational users and vacationers – want Shinnecock to be restored to its previous glory, with lush seagrass meadows, clear waters, and loads of clams, crabs, and fish. We need to work hard to achieve this goal. Shellfish restoration will help, but other means are necessary for restoring water quality. Whether that’s sewering the east end, and building tertiary treatment plants, or somehow increasing ocean flushing to the more isolated portions of the bay remains to be seen. However, if everyone involved is as invested as they claim, and that will be the ultimate test, restoration is possible.
Judge, M., L. Coen, and K. L. Heck. 1993. Does Mercenaria mercenaria encounter elevated food levels in seagrass beds? Results from a novel technique to collect suspended food resources. Marine Ecology Progress Series 92:141-150
Irlandi, E. (1996). The effects of seagrass patch size and energy regime on growth of a suspension-feeding bivalve Journal of Marine Research, 54 (1), 161-185 DOI: 10.1357/0022240963213439
Irlandi, E. (1997). Seagrass Patch Size and Survivorship of an Infaunal Bivalve Oikos, 78 (3) DOI: 10.2307/3545612
Dennison, WC, Marshall GJ, & Wigand, C (1989). Effect of “brown tide” shading on eelgrass (Zostera marina) distributions in: Novel Phytoplankton Blooms: Causes and Impacts of Recurrent Brown Tides and Other Unusual Blooms, 675-692
Cerrato, R., Caron, D., Lonsdale, D., Rose, J., & Schaffner, R. (2004). Effect of the northern quahog Mercenaria mercenaria on the development of blooms of the brown tide alga Aureococcus anophagefferens Marine Ecology Progress Series, 281, 93-108 DOI: 10.3354/meps281093
Bricelj, V., & MacQuarrie, S. (2007). Effects of brown tide (Aureococcus anophagefferens) on hard clam Mercenaria mercenaria larvae and implications for benthic recruitment Marine Ecology Progress Series, 331, 147-159 DOI: 10.3354/meps331147
Newell, R., Tettelbach, S., Gobler, C., & Kimmel, D. (2009). Relationships between reproduction in suspension-feeding hard clams Mercenaria mercenaria and phytoplankton community structure Marine Ecology Progress Series, 387, 179-196 DOI: 10.3354/meps08083
Or – What do I do when field observations don’t match lab results. This is a philosophical debate that has plagued ecologists for decades and it brings up all sorts of issues – relevant scale, extrapolation, replication and pseudoreplication, variable control, realism, and the list can go on and on. How did I arrive at the crux of this debate?Cochlodinium polykrikoides. It is a harmful algal species, now a common annual occurrence in Long Island, NY, whose blooms are known to be ichtyotoxic, and more recently, to be potentially devastating to shellfish as well. Now I am not a harmful algae person by any stretch of the imagination, but many of my colleagues are, and I often find myself engaged in healthy debates with them over the utility of lab vs field experiments.
Image from Chris Gobler
Why? Well there is a body of literature that suggests C. polykrikoides is harmful to a number of shellfish species. In fact, chronic exposure in the lab has led to high mortality and depressed growth rates of juvenile bivalves. Other studies demonstrate rapid mortality of bivalve larvae in lab exposures over periods as short as 24 hours. Lab experiments have proved especially useful in determining the mechanism of toxicity, and determining how dense blooms should be to have particularly devastating impacts. The Gobler lab at the School of Marine and Atmospheric Sciences at Stony Brook University is at the forefront of many of these studies.
Again, I am not a harmful algae person, so why do I care about this? Well, my study organism, the bay scallop, can be affected by these blooms. That, and the fact that millions of dollars have been invested to restore bay scallop populations in NY waters. The earliest research of these blooms out of New York (where they first appeared in 2002 and have recurred annually since 2004) indicated harm for bay scallops. Using 5-l plastic buckets and bloom water collected from the field, Gobler and others (2008) demonstrated up to 75% mortality of juvenile scallops (~11mm shell height) after 9 days of exposure. Additionally, this stud demonstrated a significant impact on scallop growth rates, being half in the bloom water as in controls – so even those scallops that survived were not doing well.
Other studies out of the lab have showed something even worse – up to 100% mortality of scallop larvae over relatively short time scales during the lab study. In well plates, Gobler and Tang utilized 10 ml of varying bloom densities of C. polykrikoides or a control consisting of T-Iso (Tahitian isochrysis) . In this study, with 20 larvae in each 10-ml well, the highest CP cell densities, >2000 per ml, caused rapid 100% mortality of bay scallops, within 10-24 hours. This is clearly problematic, as blooms occur when scallop larvae are expected to be in the water, so this has potential to be devastating to the restoration effort.
Figures from Gobler et al 2008 and Tang and Gobler 2009
If we extrapolate based on these results, we would expect extremely low recruitment and abundance of bay scallops. In fact, the Gobler et al paper from 2008 says exactly that: “Our results demonstrate that the failure of this population to recover could be due, in part, to recent outbreaks of C. polykrikoides blooms in this system.” Wow. Has that for scaling up! What’s the problem here? Well, first and foremost, the statement is fundamentally false. Anyone who has been following this blog can attest to the fact that scallop populations are indeed recovering. The most recent literature shows over 13-fold increases in on bottom densities of scallops in restored basins – see Tettelbach and Smith, 2009. And a manuscript we are currently finishing shows even better results. Landings have been increasing as well, as demonstrated here:
Data from Steve Tettelbach
In addition, as an unexpected natural experiment of sorts this summer, I was able to observe scallop recruitment in the presence of C. polykrikoides, which means the scallop larvae survived, remained competent, settled, grew, and survived all in the presence of this harmful algal blooms. This is preliminary data still, and remember, I was not looking for this relationship. In fact, I was simply interested in monitoring scallop recruitment in Shinnecock Bay, a south shore lagoon, with healthy eelgrass populations (and eelgrass is the preferred scallop habitat, although other habitats are also important). That was my goal. Being interested in all things, I thought it would be useful to have an idea of size fractionated chlorophyll analysis for each of my Shinnecock Bay study sites, to see what the differences might be across the bay. Additionally, I collected water that I fixed with Lugol’s so I could have an idea what the phytoplankton community looked like. As a part of this process, I was able to get CP cell densities at the same sites which I collected scallop recruits.
So what gives? Well, I think that its clear that lab experiments can’t be so easily extrapolated to the ecosystem level. And maybe, we shouldn’t even attempt to extrapolate these data to ecosystem scale processes. Lab experiments are good because they are extremely reproducible, can rapidly generate data, regulate all independent variables, and are lend toward easy replication. However, they have limitations in both spatial and temporal scale, realism and generality. So while larvae in 10 ml of high concentrations of CP all die within 24 hours in the lab, the likelihood that that kind of exposure happens in the field is extremely unlikely. Even the 5-l bucket experiments were unrealistic. The lab experiments failed to incorporate physical and biological characteristics of the system. Things such as larval availability, larval behavior, algal behavior, water column depth, variations in temperature, daylight, salinity, the community, etc, are all ignored in the lab experiments.
However, by its very nature, CP is difficult to study in the field. It is a spatially aggregating, chain forming species – so that over the spatial extent of the bloom you can experience cell densities that vary by orders of magnitude. It also undergoes diel vertical migration, so that it is at the surface during the day and the bottom at night (where exactly they go at the bottom is another story). It just can’t be controlled in the field and its spatial extent and bloom density is highly variable and unpredictable. So figuring out the problems with the lab exposures is not as simple as placing some scallops out in the field. So its a question that is not easily solved, which is probably why it is still being debated after decades.
Image from C. Gobler
In case you couldn’t tell, I am a field ecologist by trade, so I am obviously a little biased. But I do personally believe that lab experiments, while important, have limited utility in ecological studies without appropriately scaled field studies to corroborate the results. Many times, microcosm studies don’t. I am not as bullish on lab studies as Stephen Carpenter (1996) who suggests “an ecologist who isolates organisms in bottles may not be working on communities and ecosystems in any relevant sense.” I think that microcosms and lab experiments have their place – and that they provide valuable information for ecological studies, and I do employ them on a limited basis. It is just in my strong opinion that their value becomes limited without field testing the results.
Either way, it is certainly an interesting debate. Both sides have valid arguments – reproducibility, replication, control in lab experiments, the realism, relevant scales, and generality in field and natural experiments. The ideal combination of lab and field experiments depends on the questions asked and species studies. But it is clear that at times, the field observations don’t match what would be expected from lab experiments. This doesn’t mean either side is wrong, but illustrates the need to utilize both practices.
EDIT – This blog post is not intended to suggest harmful algae don’t have impacts in the field. There are plenty of examples from the field of harmful algae having impacts on fauna – including the recent sardine die-off in California. Rather, it is only to illustrate disconnects between field and lab observations.
Carpenter, S. (1996). Microcosm Experiments have Limited Relevance for Community and Ecosystem Ecology Ecology, 77 (3) DOI: 10.2307/2265490 Gobler, C., Berry, D., Anderson, O., Burson, A., Koch, F., Rodgers, B., Moore, L., Goleski, J., Allam, B., Bowser, P., Tang, Y., & Nuzzi, R. (2008). Characterization, dynamics, and ecological impacts of harmful Cochlodinium polykrikoides blooms on eastern Long Island, NY, USA Harmful Algae, 7 (3), 293-307 DOI: 10.1016/j.hal.2007.12.006 Tang, Y., & Gobler, C. (2009). Cochlodinium polykrikoides blooms and clonal isolates from the northwest Atlantic coast cause rapid mortality in larvae of multiple bivalve species Marine Biology, 156 (12), 2601-2611 DOI: 10.1007/s00227-009-1285-z Tettelbach, S., & Smith, C. (2009). Bay Scallop Restoration in New York Ecological Restoration, 27 (1), 20-22 DOI: 10.3368/er.27.1.20
Lionfish from my Fiji dive trip. It was upside down under a coral ledge
So wow. I’m not saying it has anything to do with me, but I made a post about lionfish a few months back, and had a very special guest blog by colleague Amber Stubler about her experience capturing lionfish with a spear gun and eating them. A commenter was concerned about that post, indicating that some research is showing that lionfish may contain ciguatera poisoning, so I had already decided to do a new post about that. But then, in the last 2 days, lionfish are making the news – first in Florida, then in the US Virgin Islands.
In Florida, dive master Randy Jordan of Emerald Dive Charters is the self-proclaimed “lion-tamer.” He has caught 331 lionfish to date, including his most recent haul, a 16 inch (!) 2 and a half pound fish. According to Fishbase, thats about as big as they get. According to the article, Jordan is scheduled to give a lecture on the subject on February 26th at the Loxahatchee River District meeting to talk about his special device to catch these invaders.
Then just yesterday, an article about the invasion problem in the USVI, where the lionfish now number in the thousands. The governing agencies there are planning meetings with divers, fishermen and businessmen to discuss the problem and how to combat it, and, in particular, to get divers and fishermen to report their kills. The worry is that these invasive voracious predators will wreak havoc on the local reefs and hit the major tourism industry.
Lionfish are getting a lot of attention currently. And I have advocated the consumption as an eradication plan. But as I mentioned, commenter John Rubattino from the USVI had commented his concerns about ciguatera poisoning being prevalent in fish caught there. This would create a major problem, as ciguatera is a food poison, and when humans consume fish that contain the toxin, they often experience nausea, vomiting, diarrhea, pain, dizziness, vertigo, chills, rashes, and other symptoms.
So how does one get ciguatera poisoning? Again, its a food poisoning which results from eating large predatory tropical fish which contain the poison. According to the CDC, these fish include barracuda, certain snappers and groupers, jacks, king mackerel and hogfish. But where does the toxin come from, since these fish don’t produce it themselves? Tiny microalgae. In particular, this toxin is produced by a harmful dinoflagellate known as Gambierdiscus toxicus. When it grows, it often settles on reef structure and macroalgae where it is consumed by herbivores and small predators. Then these fish are consumed, and so on and so forth up the food chain. But the toxin is not harmful to the fish. So the large predators listed above contuinue to accumulate (a process known as bioaccumulation, also here, one of the reasons why you shouldn’t eat too much tuna or many other fish due to mercury) the toxin. Then, when humans eat those fish, they get extremely ill.
So I did some research on the itnerwebs about lionfish and ciguatera. Lionfish already produce their own toxin, present in their spines, but the thought was as long as they were processed carefully, that would not be harmful to humans. Surprisingly, there is little information about lionfish and ciguatera. There are a few posts from the Caribbean Oceanic Restoration and Education (CORE) Foundation in the USVI about lionfish with ciguatera, and how to proceed. Attached 5. Ciguatera is a .pdf from the Caribbean Epidemiology Centre about ciguatera cases in the Caribbean.
So its now out there and at least something to think about. There haven’t been many reported cases, but it might be worthy of investigation in the future. Obviously, lionfish present a considerable risk to the coral ecosystems they are invading, and so eradication must be considered. A simple way is to encourage locals to fish and eat them, and hopefully fish them out. However, if they might present a risk to human consumption, this idea needs to change. Research is warranted to resolve these issues.
I am a marine biologist that is currently attending graduate school at the School of Marine and Atmospheric Sciences, Marine Sciences Research Center, of Stony Brook University, New York. I am very interested in marine ecology and have been focusing my studies on bay scallop interactions with their habitats. I plan to investigate various anthropogenic impacts on bay scallop populations for my PhD dissertation. This blog will highlight the details of my graduate research, from bay scallop-eelgrass interactions as previously mentioned, to alternative habitats for scallops, such as Codium, to trophic cascades, and more. Enjoy!
Artificial Seagrass
Is a useful experimental tool to mimic natural seagrass while controlling many factors, such as density, canopy height, leaf number, which are usually confounding in natural eelgrass meadows.
Scallops seem to love this stuff!
Judge, M., L. Coen, and K. L. Heck. 1993. Does Mercenaria mercenaria encounter elevated food levels in seagrass beds? Results from a novel technique to collect suspended food resources. Marine Ecology Progress Series 92:141-150
Recent Chronicles comments