Marine phytoplankton are a group of single-celled algae that are the primary producers in coastal and oceanic waters. Like terrestrial plants, the majority of the species of phytoplankton are photosynthetic. Under optimal combinations of sunlight, nutrients and temperature, some species grow rapidly forming “blooms” which, in most cases, has a positive influence on the marine ecosystem by enriching the entire food-web. However, some blooms produce phytotoxins which disrupts ecosystem function, can cause mortalities of birds, fish, and marine mammals, and can disrupt the local economy and human health by contaminating shellfish. These toxic phytoplankton blooms are termed Harmful Algal Blooms (HAB) and they are actually caused by only a few species of phytoplankton.
Timing of phytoplankton blooms
In the coastal waters off Oregon, phytoplankton can be productive from February through October/November. The richest blooms occur from April through October, because wind-driven upwelling brings nutrient-rich deep water to the upper water column which fuels large phytoplankton blooms. The timing, magnitude, and species composition of a bloom determines its subsequent effects on other organisms and the food web. We track the progress of phytoplankton blooms through our biweekly sampling cruises off Newport, Oregon.
The phytoplankton species off Newport Oregon cover a broad size range from nano- (2-20μm) to micro- (20-200μm) algae. Diatoms are the most dominant micro-sized taxa responsible for nearly all of the bloom events that occur during upwelling, but occasionally dinoflagellates dominate. In the ocean, diatom species are most commonly present in the shape of long chains (e.g. several mm in length) or colonies (Figures 1-4).
Harmful Algal Blooms (HABs)
The major phytoplankton taxa that cause HABs in the Pacific Northwest are the diatom Pseudo-nitzschia (PN, Figure 5) and the dinoflagellate Alexandrium catenella (Figure 6). Domoic acid (DA) produced by PN can cause Amnesic Shellfish Poisoning (ASP). Saxitoxins (STX) are produced by several dinoflagellates, including Alexandrium, and they cause Paralytic Shellfish Poisoning (PSP).
Although PN blooms can occur annually with the onset of the upwelling season, these PN blooms aren’t always toxic. This year, we have seen the spatially largest PN bloom and DA toxin production along the west coast, spanning from central California to British Columbia, leading to extended shellfish closures and deaths of marine mammals.
The mechanisms triggering significant DA production are attributed to both external environmental stress and internal biophysiological reactions, which varies by strain/species and region. In contrast, while Alexandrium are mostly found in lower numbers, once their cells are present in the water, their toxic effects can be directly apparent.
During the juvenile salmon survey, we are not only interested in the numbers and condition of juvenile salmon, we are also interested in other organisms such as marine birds and mammals that interact with, and might prey upon, juvenile salmon. Because most marine birds and mammals depend upon small fish, krill, or squid for their primary food supply, knowing where these animals are gives us a window into where the productive areas of the ocean are. To better understand this, each morning we count marine birds and mammals on our survey lines.
The work begins at dawn. One person counts while a second person records counts into a computer program that adds a time, date, and exact location with each observation. In our study area, it is normal for only two species to make up over 80% of the birds we see nearshore in summer. These two species are the sooty shearwater, an albatross relative which migrates here all the way from Chile and New Zealand; and the common murre, a puffin relative which nests on the bare rock of cliffs and sea stacks in northern temperate seas. It can be very exciting when you come into groups of thousands of hunting birds churning up the water in a feeding flock - it literally looks like a tornado of activity.
What was a bit unusual during the June 2015 survey were the apparently large numbers of pink-footed shearwater (a member of the albatross family that also migrates here all the way from Chile, where there are only three known breeding colonies), Cassin’s auklets (a small member of the puffin family), and humpback whales.
The diet of pink-footed shearwaters is a bit of a mystery, but they probably eat squid and small fish. While, Cassin’s auklets depend exclusively on krill and other large plankton, and humpbacks consume both krill and small fish.
We encountered dozens of humpbacks during our survey, most putting on quite a show all day long – slapping their tails and large front flippers, and jumping out of the water in spectacular, ship-soaking, full-body breaches. We also were graced with visits from many smaller whales like Pacific white-sided dolphins, who were apparently trying to outdo the humpback show; and Dall’s porpoises, who came over one evening to surf on the bow-wake created by the FV Frosti.
Pacific white-sided dolphins (Lagenorhynchus obliquidens): Here is a Movie showing off their bow-riding prowess on a calm evening at sea. Many dolphins and porpoises ride the pressure waves created by boats moving forward in the water. It is thought that marine mammals bow-ride for the same reason human surfers surf – it’s a heck of a lot of fun, and a way to show off for your buddies!
Dall’s porpoises (Phoecenoides dalli): Movie of them catching a ride on the bow of the Frosti. These porpoises have a striking, hourglass-shaped black-and-white pattern on their bodies, and are thought to be the fastest-swimming of all the small whales – up to 55 km per hour. Bow-riding is a form of play that hones key swimming skills: you have to be fast, maneuverable, and work as a team to successfully catch enough fish to make a living.
Juvenile salmon catches
We have completed another very successful juvenile salmon survey. We conducted 45 fish trawls over 8 days of sampling and captured mostly juvenile coho and Chinook salmon. We also caught juvenile chum and sockeye salmon, as well as a few steelhead and cutthroat. There are seven species of native salmonids in the Northern California Current. We caught 6 of the 7 species; the only species we didn’t catch on this survey was pink salmon!
These juvenile salmon catches are a part of our Ocean ecosystem Indicators suite of data that provide outlooks for adult salmon returns to the Columbia River. This year, the catches of juvenile Chinook salmon were on the lower side of our 18 year time series, while the catches of juvenile coho salmon were about average.
Juvenile salmon condition
The condition of the juvenile fish is another important measure of how these salmon are faring. Condition, in this case, means how “fat” or “skinny” a given fish is for its length. “Fatter” fish have a better chance of survival. During this survey, we noted that the juvenile Chinook salmon looked in relatively good condition, while in general the juvenile coho salmon tended to look like they were in poorer condition. We will have to wait until these fish are necropsied (dissected) in our lab in order to see if our visual observations during the survey are correct.
Harmful Algal Bloom
The Harmful Algal Bloom (HAB) off the west coast was in full swing during our survey and our zooplankton samples were brown and gooey and difficult to filter. We also collected smaller samples to look for the harmful algae. Here are some HAB samples from Queeets River, WA, ranging from stations 3 to 24 nautical miles offshore and you can see how the bloom is most intense closer to shore.
Another interesting finding that we have not observed over the past 18 years was a change in the jellyfish species composition. We always catch a large number of the sea nettle jellyfish (Chrysaora fuscescens). However, this June, the sea nettles were almost entirely absent from our samples and instead we caught unpreceded numbers of the water jelly (Aequorea sp., photo).
This has been seen by other surveys this summer off of California and southern Oregon, but we are unclear why. During previous surveys, we find that the water jelly is associated with warmer water, therefore their high abundance this year might be linked to the warm ”blob” of water that is still persistent in the northern Pacific ocean.
Marine Birds and mammals