Click on the images to view larger versions.
For the past 6 days, I have been quite fortunate to experience my first offshore cruise in the Northwest Atlantic Ocean aboard the CCGS M. Perley – a Canadian Coast Guard research vessel. This is not my first time away from land – I’ve conducted research from fishing vessels in the Bay of Fundy and from zodiac in the Bras d’Or lakes. Even as a kid growing up in a small fishing community I was exposed to the sea, frequenting fishing vessels owned by friends’ parents. However, this was my first time venturing a substantial distance offshore on a large research vessel to sample the benthic diversity associated with the NW Atlantic.
As a recently hired biologist at Fisheries and Oceans Canada in Moncton, New Brunswick, I was offered the chance to assist in an annual (but temporary) scallop survey off the northern coast of New Brunswick. The five-year-long survey has been established since 2012, with this year being the last year of the survey. A bottom trawl is used to collect benthic samples. We trawled for 2 minutes at each site and organisms brought up were sorted, identified, counted, weighed, and measured on deck in between drags. This made for intensive 12 hour days, but the data alone provided enough currency and motivation to keep me going.
While the cruises are dedicated to assessing scallop populations off the coast of New Brunswick, data on a slew of other benthic species are collected. Indeed abundances and biomass of all collected species are recorded, along with other basic morphometrics of other key species (e.g. carapace morphometry of crabs and lobsters, and lengths of fishes). We also had a CTD on board, equipped with probes to measure depth, conductivity, temperature, salinity, dissolved oxygen, and pH.
The experience was nothing short of spectacular. I’ve come to note that sunrises and sunsets are much more appealing from sea. The diversity of animals was astounding and unpredictable from trawl to trawl – crustacaens, cnidarians, echinoderms, molluscs, poriferans, and fishes were all apparent in multiple trawls. The most common species were crustaceans. Shrimps (Argis dentata, Pandalus borealis, Pandalus montagui, and Sclerocrangon borea) and rock crabs (Cancer irroratus) really dominated the trawls.
Closer to shore, lobsters (Homarus americanus) were quite abundant as well, while an abundance of snow crabs (Chionoecetes opilio) and toad crabs (Hyas araneus and Hyas coaractatus) were frequent at more offshore sites – in one trawl we hauled up >80 snow crabs! We also recorded quite a few Acadian hermit crabs (Pagurus acadianus).
In some of the trawls, a vast array of other species were evident. Echinoderms were also abundant. Sea cukes (Cucumaria frondosa, Psolus fabricii), urchins (Strongylo- centrotus droebachiensis), sand dollars (Echinarachinus parma), sea stars (Asterias spp., Crossaster papposus, Henricia sanguinolenta, Leptasterias polaris, Solaster end- eca), and brittle stars (Ophiopholis aculeata) were quite abundant in many trawls – we even saw a couple of large basket stars (Gorgonocephalus arcticus)!
A number of bivalves were also present, including clams (Arctica islandica, Cyclocardia borealis, Cyrtodaria silique, Mactromeris polynyma, Serripes groenlandicus, and Yolida sp.,), scallops (Chlamys islandica, Placopectin magellanicus), and horse mussels (Modiolus modiolus). Similarly to bivalves, brachiopods were abundant at a number of sites. We also observed a number of gastropods (Buccinum undatum, Neptunea decemcostata, Colus stimpsoni, Aporrhais occidentalis, Lunatia heros) and chitons were abundant at a number of stations. Less common were sponges, jellyfishes, and sponges. Tube worms (Polychaeata) dominated the deeper muddy zones (>50 m depth).
Fishes were also present in a number of trawls. Species observed included American plaice (Hippoglossoides platessoides), Arctic alligatorfish (Ulcina olrikii), Atlantic poacher (Leptagonus decagonus), cunner (Tautogolabrus adspersus), fourline snakeblenny (Eumesogrammus praecisus), yellowtail flounder (Limanda ferruginea), winter flounder (Pseudopleuronectes americanus), longhorn sculpin (Myoxocephalus octodecemspinosus) shorthorn sculpin (Myoxocephalus scorpius), grubby (Myoxocephalus aenaeus), lumpfish (Cyclopterus lumpus), ocean pout (Zoarces americanus), sea raven (Hemitripterus americanus), and sand lance (Ammodytes sp.)
Of course other species have been observed on trawls that I have not attended. The above list is nowhere near exhaustive, but is an overview of the species that I observed during my time on the M. Perley. The experience was fantastic, and I look forward to the next opportunity to get back to a place with a flat horizon.
Until then, it’s back to manuscripts and grant proposals…
When assessing the impacts of ocean acidification (OA) on marine animals, peer-reviewed studies predominantly address the mortality and physiology of these organisms. However, over the past few years, it has become apparent that animal behavior can also be altered under increasingly acidifying conditions.
A recent study by Sue-Ann Watson and colleagues at James Cook University in Australia demonstrated that near-future CO2 levels can interfere with neurotransmitter functioning (i.e., chemical functioning of the brain), leading to a 50% decrease in predatory escape behavior in a species of marine gastropods, making them more susceptible to being eaten by predators in high-CO2 conditions. Studies have also suggested shifts in the behavior of various fishes, including increased anxiety in rockfish, hindered hearing behavior in clownfish, and reduced swimming behavior in dolphinfish, with the likely mechanism being hindered neurotransmitter functioning. Some of these observations in fishes have also been translated to invertebrate organisms as well. Alongside these behavioural modifications under acidic water-column conditions, some interesting research on the east coast of North America has also been suggesting that juvenile clams can change their behavior in response to increased acidification as well, except in this case, the clams respond to sediments and not the water column.
Before they mature and dig into sediments at the bottom of the ocean in coastal areas, clams go through what is called a larval stage, where they swim around and develop in the water column (this is akin to a caterpillar and a butterfly – the caterpillar is the larvae and the butterfly is the mature). After a certain period of time, the larval clams will sink to the bottom to start their life as mature animals. However, before they dig into the sediment to start the next stage of their life, they can test the chemistry of the sediment and make a decision as to whether or not it is an appropriate place to live. So if they don’t like the initial place where they land, they can refuse to burrow into it and may be able to move to a different area.
Recent research has suggested that the acidification of these sediments may impact the behavior of these clams in their decision to dig or leave. One study conducted by Mark Green and colleagues at St. Joseph’s College in Maine, USA assessed the impact of increasing acidification within marine muds on the burrowing behavior of juvenile quahogs (Mercenaria mercenaria).
By manipulating the level of acidity in different containers of soft-sediment and watching whether or not clams burrowed into them, the scientists were able to determine that as the sediment becomes more acidic, the clams reject it and don’t burrow – the first time that acidification was found to have an impact on clam burrowing behavior.
Given this interesting result, researchers at the University of New Brunswick in New Brunswick, Canada wanted to see if this lack of burrowing actually resulted in the clams moving away. By taking the same approach as Green and colleagues, only with a different species of clam (soft-shell clam, Mya arenaria), myself and Dr. Heather Hunt (see “Publications” to download a PDF) observed the same trend of burrowing behavior that Green and colleagues did in their study – more acidic sediments had less clams burrowing. However, by adding flowing water to the experiments (a means by which soft-shell clams move), we were able to determine that when sediment was more acidic, more clams left than when sediment was not as acidic.
The combined results of our study and those of Green and colleagues provide evidence that the acidification of marine soft-sediments can influence the behavior and population dynamics of juvenile clams by altering their decision to burrow and subsequently their dispersion. Since acidic conditions dissolve the shells of these animals and result in death, this could be the reason why the clams decide to move away from these acidic muds. Other reasons are possible, however. For example, increased concentrations of CO2 may depress other physiological functions such as respiration, metabolism, or feeding, which would also contribute to the negative burrowing cue (recruitment cue) detected in these two studies.
These studies, along with others, highlight the impact of ocean acidification on the behavior of marine-dwelling animals. Changes in behavior have the potential to impact these animals in both positive and negative ways.
The bright side, at least for clams, is that if they can avoid more acidic sediments and move to better ones, they enhance their chances of avoiding “death by dissolution” or other stressful conditions, so long as there is enough suitable mud available! However, by not burrowing immediately, the clams do put themselves at a higher risk for other mortality factors, such as predation. Ultimately, scientists have much work to do in determining how the future chemistry of our oceans could impact the behavior of marine organisms and how this could in turn influence their survival.
Known as “the other CO2 problem”, ocean acidification (OA) has crept onto the scene as one of the most menacing and destructive aspects of human-induced climate change. Basically, OA refers to the dissolving of atmospheric carbon dioxide (CO2) into the oceans, making them more acidic and spelling trouble for many marine organisms, particularly those with calcium carbonate (CaCO3) skeletons (e.g., pteropods, clams, snails, corals). Since the Industrial Revolution, the pH of the oceans has dropped from ~8.2 to ~8.1, corresponding to a 30% increase in ocean acidity, with a projected 0.3-0.4 further decrease by 2100 (120-150% increase in acidity). Ultimately, OA could result in major losses to marine biodiversity, threatened food sources for a myriad of organisms (including humans), diminished coastal protection, altered food webs and ecosystem structuring, and an interrupted carbonate system (Hardt & Safina 2008). However, OA is typically attributed to the burning of fossil fuels and the human contribution to atmospheric CO2. As a result, this can be misleading when reporting the effects that ocean acidification is having in coastal waters and those that it could have in the near future.
Recently, open-ocean acidification has been distinguished from that of coastal waters on the basis that acidification in coastal regions is functionally much different than that of the open ocean (Duarte et al. 2012). As a consequence, the pH decrease in coastal waters (particularly in estuaries) is much more pronounced than that of the open-ocean, and the variability of pH ranges is much wider. Furthermore, although atmospheric CO2 is the primary driver in open-ocean acidification, it plays less of a role in coastal systems. Instead, coastal upwelling, terrestrial and freshwater runoff, organic decomposition, and other processes not occurring in the open-ocean can act as the primary drivers of acidification in coastal systems to varying degrees. As such, organisms residing within coastal waters are subjected to extremely stressful conditions for the majority of their life.