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Winter 2020
Zooming in on Marine Microorganisms (Part 2)
This is part two of a two-part series on marine microorganisms.
By Jerilyn Ritzman, WSU Extension Island County Shore Stewards Program Coordinator.
Figure 1: A bloom of the dinoflagellate noctiluca in Puget Sound in May 2019. While noctiluca
itself is not toxic, blooms of noctiluca can disrupt the food web as they consume plankton
that are important food sources for other animals such as juvenile fish. Image Credit: Eyes
over Puget Sound / Permitted use as free educational material. Washington State
Department of Ecology (link).
Introduction
Our last newsletter highlighted five common types of marine microorganisms: coccolithophores, diatoms,
cyanobacteria, dinoflagellates, and foraminifera. It covered their histories dating back hundreds of millions or
even billions of years as well as their roles in supporting the marine food web, oxygen production, or the carbon
and nitrogen cycles. While all of these functions are critical to life as we know it, marine microorganisms can
also present significant threats to marine and human health. Likewise, human activity can also threaten the
health of marine microorganisms and thus the entire marine food web. This newsletter will address these
interactions between humans and marine microorganisms, using examples from Puget Sound and the U.S. West
Coast, and also what Shore Stewards can do to lessen these impacts.
When marine microorganisms aren’t so invisible
Although we don’t notice marine microorganisms often in our daily lives, there are instances when their
presence is felt more directly in Puget Sound and other nearby waters.
Algal blooms and hypoxia
Occasionally, changes in water conditions including temperature and
nutrient levels can cause a dramatic increase of certain marine
microorganisms known as algal blooms. If the particular bloom in
question is harmful to other species, then it is known as a harmful
algal bloom (or “HAB”). Sometimes these blooms are visible as
discoloration in the water. The term “HAB” is favored now over the
more familiar term of “red tide” because not all harmful blooms are
red/visible in the water and not all visible blooms are harmful.
During summer months, coccolithophores occasionally form
dramatic turquoise blooms in areas of the Pacific Northwest such as
Hood Canal. The vibrant color in the water is caused by how sunlight
reflects off their microscopic plates called coccoliths. While the
coccolithophores themselves are not toxic, their death and
Figure 2: NASA’s Landsat 8 satellite captured this
decomposition can deplete the water of dissolved oxygen, creating a
image of a massive turquoise algal bloom in Hood condition known as hypoxia, with potentially dangerous
Canal. Image Credit: NASA Earth Observatory Image consequences for fish and shellfish. In Hood Canal, this situation can
of the Day for July 29, 2016 by Jesse Allen, using
Landsat data from the U.S. Geological Survey / Public
be exacerbated by the length and shape of the channel itself, which
Domain (link). slows water circulation.
Shellfish poisoning and harvest closures
Some species of marine microorganisms produce toxic chemicals, either on their own or indirectly through their
death and decomposition or through interactions with other microorganisms. Blooms of these species can raise
toxin concentrations in the water to levels dangerous to humans and other animals, who can be exposed
through contact with contaminated water or through consumption of contaminated fish or shellfish. Shellfish
in particular can accumulate toxins in their flesh that exceed the levels found in the surrounding water and
persist long after an algal bloom has subsided. The symptoms of fish or shellfish poisoning depend on the species
of microorganism, and include paralytic shellfish poisoning (PSP), amnesic shellfish poisoning (ASP), and
diarrhetic shellfish poisoning (DSP). Many algal toxins are odorless, tasteless, and heat-resistant, and accidental
ingestion can require hospitalization or even be life threatening.
The health effects of toxic algal blooms are not the only risk posed to humans; the measures we take to avoid
exposure to algal toxins can have their own repercussions. For example, a massive bloom of the diatom Pseudo-
nitzchia along the U.S. West Coast in 2015 led to high concentrations of the neurotoxin domoic acid (responsible
for ASP) in shellfish such as Dungeness crabs and razor clams. This event prompted closures of both commercial
and recreational harvesting operations, negatively impacting some fishing communities both economically and
socially through the loss of long-held traditions. These types of blooms are not limited to the outer Pacific coast;
temporary shellfish harvest closures have been instituted in the past in Puget Sound. There is evidence that
harmful algal blooms can become more common as climate change warms ocean waters, which means they
may pose increasingly serious risks to coastal communities.
Bioluminescence
Not all close encounters with marine microorganisms need to be negative. As
mentioned in the previous newsletter, dinoflagellates can produce beautiful
displays of bioluminescence. This phenomenon can be seen around Puget
Sound, but is most common during summer months when the waters are
warmer. These displays are best viewed in the darkest conditions, well after
sunset and on moonless nights, so take safety precautions if you’re going out
on the water to view them. Remember that the waters need to be churned to
produce the light show, such as by waves’ breaking on the shore or by the
paddle of a kayak. If you’re less experienced on the water and still want a front Figure 3: Agitated waters such as those
row seat to nature’s aquatic light show, some local companies offer nighttime along shorelines can provide
opportunities to view bioluminescence.
kayak tours in the summer. Image Credit: Jed Sundwall / CC-BY-SA-
2.0. Wikimedia Commons (link).
Human impacts on marine microorganisms
Marine microorganisms may be tiny, but they are not immune to the many ways in which humans influence the
environment. While these impacts can be difficult to study, they can be of profound importance to
understanding the risks that human activity poses to marine environments as a whole.
PCBs and other toxic chemicals
Figure 4: After entering the food web through marine microorganisms, contaminants like
PCBs and DDT can be passed upwards to larger and larger predators, where they can
concentrate to potentially dangerous levels. Image Credit: Øystein Paulsen / CC-BY-SA-
3.0. Wikimedia Commons (link).
The waters of Puget Sound are home to a cocktail of toxic chemicals largely as a result of human activity since
the industrial revolution. This unsavory roster includes polychlorinated biphenyls (PCBs) from electrical
equipment, polybrominated diphenyl ethers (PBDEs) used as heat retardants, copper from automobile brake
pads, and zinc from tire abrasion. Marine microorganisms are often the first stop for these chemicals after they
enter Puget Sound as many toxins are hydrophobic, meaning they prefer to attach themselves to solid particles
instead of staying dissolved in water. When these pollutants embed themselves in marine microorganisms, they
can be carried upward through the food web where they concentrate in larger animals like fish, whales, and
even us humans. This phenomenon is known as bioamplification (or biomagnification) and it can lead to toxin
concentrations high enough to cause metabolic distress, disrupt the immune system, and hinder reproduction.
To make matters worse, PCBs are slow to break down and can recycle through the food web many times as
organic matter containing PCBs decomposes and releases the PCBs back into the water.
Nutrient inputs
Like any living thing, marine microorganisms need nutrients to survive. Two of the most important nutrients for
phytoplankton – dissolved nitrogen and phosphorus – are delivered naturally to the Puget Sound, largely by
upwelling currents from the Pacific Ocean. However, an excess of nutrients from human activity can upset the
balance of phytoplankton communities and create conditions favorable for harmful algal blooms. These blooms
can block sunlight that other organisms need, and their death and decomposition can contribute to other
phenomena mentioned in this section, such as hypoxia and ocean acidification. In the most extreme cases,
nutrient overload and algal blooms can create underwater “dead zones” where very few species can survive.
Human activities known to increase nutrient loading include faulty septic systems, pet waste, runoff from
agricultural operations (many fertilizers contain nitrogen), and effluent from sewage treatment plants. Most of
these sources are expected to increase as the human population of Puget Sound, currently over 4 million, is
expected to grow by another 1.8 million by 2050, leading to an estimated 40% more nutrients. The dependence
of the food web on healthy plankton communities is only beginning to be understood, but excess nutrient
loading appears to present an ongoing challenge to maintaining healthy plankton communities here and along
much the world’s developed coasts.
Ocean acidification and higher sea temperatures
Figure 5: Although slightly larger than the microorganisms covered
in this series, this pteropod shell provides a good illustration of how
ocean acidification can impact organisms that use calcium
carbonate to create their shells. This pteropod was placed in
seawater mimicking projected acidity levels in the year 2100 and
the dissolution occurred in 45 days. Image Credit: NOAA
Environmental Visualization Laboratory (EVL) / Public Domain.
Wikimedia Commons (link).
Ocean acidification is a trend associated with global climate change, where dissolved carbon dioxide alters the
carbonate chemistry in seawater and increases its acidity. Surface ocean water is estimated to be about 30%
more acidic today than it was in 1750 and is predicted to rise to 100-150% higher in 2100 compared to 1750 if
current rates continue. High seawater acidity can make life difficult for marine creatures that create calcium
carbonate shells, including shellfish and many marine microorganisms, and can even dissolve shells under
certain conditions. Conversely, higher concentrations of dissolved CO2 can be advantageous for other marine
microbes, including some species of phytoplankton, that utilize it during photosynthesis.
The impacts of ocean acidification on marine microorganisms have been observed already but are difficult to
predict in the future. The oceans are part of a complex and dynamic system, and increased ocean acidity will
likely be accompanied by increased ocean temperatures, disrupted currents, and changes in upwelling behavior.
This will likely lead to divergent outcomes for different species of microorganisms, where not all species are
impacted in the same ways, if at all. However, this divergent impact on different species of marine
microorganisms could lead to changes in the structure of marine food webs or the cycling of different elements,
leading to unpredictable outcomes. High acidity can be further exacerbated locally by certain types of pollutionand the decomposition of organic matter, and it is particularly acute in Washington State, where upwelling
offshore waters carry additional dissolved CO2 to the surface.
Plastic
Despite their small size, plankton are not immune to the effects of
ocean plastic and can even provide a pathway for the pollution to
reach higher levels of the food web. For example, larger
zooplankton that are accustomed to eating other plankton can
mistake microplastic fragments and fibers for food and ingest the
plastics instead, decreasing the amount of other plankton they
consume and throwing off natural balances of species. This change
in diet can be dangerous for the plankton themselves, with
potential impacts on nutrient uptake and reproduction, but can
also be dangerous for their predators who ingest plastic-
Figure 6: Plastic pollution often breaks down into smaller
contaminated individuals. Plastics large and small can also act as
and smaller fragments like these in the ocean (note the vehicles for microorganisms, and more research is needed to
centimeter ruler in the background). To a zooplankton, determine how these plastics might leach toxic chemicals, along
microplastics can look like a tasty meal. Image Credit:
U.S. Geological Survey / Public Domain. Microplastics in
with additives like bisphenol A (BPA), into the surrounding water or
our Nation's waterways (link). into the microorganisms themselves.
Human impacts on marine microorganisms: What we can do
Many of the threats to marine microorganisms can seem daunting to address; however, there are practical steps
we can all take in our daily lives to help encourage healthy plankton communities in our local waters. Just a few
examples include:
1. Properly dispose of pet waste, chemicals, and other substances (e.g. paint).
2. Report spills you see of chemicals, paint, vehicle fluids, etc. to the appropriate authorities (see the
Resources section below).
3. Make sure your septic system is functioning properly.
4. Make sure your car is maintained and use commercial car washes rather than wash on your property.
5. Reduce plastic use and recycle.
6. Use compost rather than store-bought fertilizers or use “slow-release” fertilizers that help prevent
excess nutrient runoff.
The U.S. Environmental Protection Agency also maintains a detailed list of actions you can take to help prevent
nutrient runoff: https://www.epa.gov/nutrientpollution/what-you-can-do.
Resources
Past editions of Shore Stewards News have addressed Harmful Algal Blooms (HAB), pet waste, shellfish safety
and related information.
In the case of oil or other hazardous waste spill:• For emergencies, call 911. For spills on water, follow the guidelines on the Dept. of Ecology's spill page.
• You can also fill out a web form to report an incident to Ecology: https://ecology.wa.gov/About-us/Get-
involved/Report-an-environmental-issue/NWRO-issue-reporting-form
• If spill does NOT reach the storm drainage system: (206) 440-4900WSDOT (state highways):
Before harvesting shellfish check the shellfish safety map (WA State Dept. of Health):
https://fortress.wa.gov/doh/biotoxin/biotoxin.html
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