Is Too Much Algae Bad for Fish?

Figure 1: Rainbow Trout (photo courtesy of the U.S Fish and Wildlife Service)

Rainbow Trout are one of the many fish species that are affected by harmful algal blooms (HABs). Harmful algal blooms occur all over the world, in freshwater and seawater, which makes them a very troubling issue. Not only do they cause damage to fish and aquatic ecosystems, but they can also negatively impact many other factors such as tourism, public health, and recreation (Gobler, 2020). Humans play a significant role in causing HABs, whether its adding extra nutrients (for example, phosphorous or nitrogen) into the water or contributing to climate change (Sellner et al., 2003). Two examples of humans adding extra nutrients into the water are agricultural runoff and industrial activity. The extra nutrients that these activities provide promotes higher rates of algae growth than usual (Sellner et al., 2003). Further, humans have contributed significantly to climate change, which raises water temperature, providing an excellent habitat for algae to live in and take over (Ho and Michalak, 2019). HABs also occur in Lake Erie, mostly in the Ohio Maumee watershed because of the agricultural practices that are dominant within that watershed.

In aquatic ecosystems, HABs cause hypoxia, which is condition where there are extremely low levels of oxygen in the water (Golber, 2020). Fish, such as the rainbow trout, do not breath air, but they still need oxygen in order to survive. The fish’s gills are huge compared to the fish’s body, which provides a lot of help when absorbing oxygen (Ness Foundation, 2019). In addition, when a fish breathes, the water flowing over the gills runs the opposite direction of the blood running through the gills, which allows the amount of oxygen in the blood to be less than the oxygen of the water (Ness Foundation, 2019). This allows oxygen to move to places where there are low amounts of oxygen, which refers to a process called diffusion. Once in the fish’s body, the oxygen attaches to a protein called hemoglobin, and it is transferred all throughout the body (Ness Foundation, 2019). Algae effect the fish’s ability to breathe by irritating the gills, which decreased the amount of oxygen that the fish receives (Svendsen et al., 2o18). If there is more algae in the water, then fish have a higher chance of suffering from this condition.

 

Figure 2: Oxygen transferred to blood via the veins as water flows through

(Photo courtesy of Charles Molar and Jane Gair, CC BY 4.0 DEED https://creativecommons.org/licenses/by/4.0/)

In order to prevent further damage caused by HABs, there has to be a reduction in agricultural runoff entering the water body. There is action being taken to minimize impacts caused by agricultural runoff, such as a reducing pesticide use, managing irrigation systems, and conservation tilling (Marsh, 2022). Industrial activity needs to be reduced or better managed to prevent nutrient-rich runoff that comes from industrial plants. The whole problem of climate change is an extremely complex problem, and there are many measures that humans can take to reduce their impact. For example, carpooling or taking the bus instead of driving most times can limit emissions from cars, which contributes to climate change. Fish are a huge part of the aquatic ecosystem, and humans need to do their part to reduce excess nutrient input into water bodies in order to protect fish.

Sources:

Gobler, C. J. (2020). Climate change and harmful algal blooms: Insights and perspective. Harmful Algae, 91, 101731. https://doi.org/10.1016/j.hal.2019.101731

Ho, J. C., & Michalak, A. M. (2019). Exploring temperature and precipitation impacts on harmful algal blooms across continental U.S. lakes. Limnology and Oceanography, 65(5), 992–1009. https://doi.org/10.1002/lno.11365

How do fish breathe? The Science Behind Gills. New England Science & Sailing (NESS). (2019, August 8). https://nessf.org/how-do-fish-breathe-the-science-behind-gills/

Marsh, J. (2022). Protecting water quality from agricultural runoff. Agrilinks. https://agrilinks.org/post/protecting-water-quality-agricultural-runoff

Sellner, K. G., Doucette, G. J., & Kirkpatrick, G. J. (2003). Harmful algal blooms: Causes, impacts and detection. Journal of Industrial Microbiology and Biotechnology, 30(7), 383–406. https://doi.org/10.1007/s10295-003-0074-9

Svendsen, M., Andersen, N., Hansen, P., & Steffensen, J. (2018). Effects of harmful algal blooms on fish: Insights from Prymnesium Parvum. Fishes, 3(1), 11. https://doi.org/10.3390/fishes3010011

The Curious Case of Disappearing Salmon

200 years ago a father and son in Washington stand along the banks of the Columbia River. They sit in silence, watching the tumbling river rush by, breathing in the fresh air and gorgeous sights. But they’re not there just to appreciate the beautiful day. In their hands, they hold twin fishing rods, though they could have walked down to the river with nothing but their hands and a bucket, and still returned flush with fish. This father and his son are fishing for Chinook salmon, a fish that migrates in schools so abundant it seems as if the river itself was made with salmon, not water. They return home, happy with a bundle of five fish each, while millions of others rush through the water. 

Just days later, another father-son pair travel to the Columbia River, but this time they’re hundreds of miles away, in Oregon. They too return home with a bountiful catch, while thousands more pass through the river unimpeded. This pattern continues all across Washington and Oregon, into California, Idaho, and watersheds across the West Coast¹.

This Chinook Population Ratings map was created using data collected and compiled by State of the Salmon – a program of the Wild Salmon Center originally launched in 2003 in partnership with Ecotrust. However, this Chinook Population Ratings map is a secondary compilation of the data and it has not been verified or authorized by Wild Salmon Center.

Over the next couple hundred years, this pattern continues, with generations of families, fisheries, and indigenous tribes depending on these fish as an integral part of their lives². The great-great-granddaughter of one of these families travels to the Columbia River with her father, just like generations before had done. But this time something is different. Though they’ve brought along their fishing rods, their bait, and anything they could need to catch salmon, the fish just aren’t biting. The river is no longer teeming with populations in the millions, the water no longer camouflaged by the countless bodies of salmon. The pair leaves defeated, with a bare catch that pales in comparison to the bounty of the years before them. 

In the last 40 years, Chinook salmon have lost 60% of their population, with some schools at 10% of their historic numbers³. There are a variety of reasons why salmon populations are struggling, from habitat loss or degradation and harvest rates to hatchery influence and dams creating new barriers³

One of the most pressing is the changing temperatures of the waters they inhabit. As the climate warms, the world’s watersheds warm along with them, with scientists projecting average temperatures to experience a 6.9°C increase by the end of the century(4). Projections estimate that the effect of increasing temperature alone could reduce populations by almost 20% in the next 40 years². The problem gets even worse in the open ocean. Salmon spend most of their life in saltwater, returning to rivers and freshwater only to breed. One study found that the dominant driver towards extinction was increasing sea surface temperature, which could lead to a 90% decline in populations, almost guaranteed extinction².

Image Courtesy of Vince Mig

Salmon are so sensitive to increasing temperatures, not just because they prefer Christmas over the 4th of July, but because their fundamental processes of life depend upon temperature. Fish are part of a group known as ectotherms, commonly referred to as cold-blooded animals. They don’t actually have cold blood, but instead rely on the external environment to dictate the temperature inside their bodies. When a human walks outside on a really hot day, something like 115℉, our body temperature stays a cool 98℉. But if a fish were exposed to those same conditions, their body temperature really would reach close to 115℉. 

In the same way humans begin to lose functioning and face potentially lethal consequences if they have a fever that becomes too high, salmon struggle to survive in high temperatures. Everyone remembers the classic fact – “the mitochondria is the powerhouse of the cell” from their middle school days. But what does that actually mean? The mitochondria are responsible for the production of a molecule known as ATP, which all the cells in your body use as their source of energy. They produce the power your cells use to function. Without ATP, death would be almost instantaneous for any living thing. The process of creating this ATP is known as metabolism. 

Metabolism is one of those biological processes that are impacted by the environmental temperature. Energy is first directed toward basic requirements for survival – things like breathing and circulating blood. Any excess energy is then able to be used to do things- move, eat, reproduce, and more. But as temperatures rise, salmon are required to put more energy into just staying alive, leaving less available for actual use(5)

 

Image Courtesy of Andrea Stöckel

¹

Pacific salmon populations across North America are dealing with the effects of heat stress – they have less energy to expend, at a time in their life when they need it the most. Without enough energy future generations can’t survive, and the results are plain to see. The great-granddaughter of our original fisher is living in a world with salmon populations that are barely an echo of the abundance they once had. Her great-granddaughter may live in a world without any salmon at all.   

Citations

  1. Salmon Life Cycle and Seasonal Fishery Planning. (2022, June 10). NOAA. https://www.fisheries.noaa.gov/west-coast/sustainable-fisheries/salmon-life-cycle-and-seasonal-fishery-planning  
  2. Crozier, L. G., Burke, B. J., Chasco, B. E., Widener, D. L., & Zabel, R. W. (2021). Climate change threatens Chinook salmon throughout their life cycle. Communications Biology, 4(1), 1–14. https://doi.org/10.1038/s42003-021-01734-w 
  3. Chinook Salmon. (2013, April 29). US EPA. https://www.epa.gov/salish-sea/chinook-salmon 
  4. Betts, R. A., Collins, M., Hemming, D. L., Jones, C. D., Lowe, J. A., & Sanderson, M. G. (2011). When could global warming reach 4°C? Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 369(1934), 67–84. https://doi.org/10.1098/rsta.2010.0292  
  5. Poletto, J. B., Cocherell, D. E., Baird, S. E., Nguyen, T. X., Cabrera-Stagno, V., Farrell, A. P., & Fangue, N. A. (2017). Unusual aerobic performance at high temperatures in juvenile Chinook salmon, Oncorhynchus tshawytscha. Conservation Physiology, 5(1), cow067. https://doi.org/10.1093/conphys/cow067 

 

Electro Sensory and Turbidity: American Paddlefish’s Decline and Outlook

Polyodon spathula

Figure 1: American Paddlefish (image courtesy of U.S. Fish and Wildlife Service)

Background:

The American Paddlefish (Polyodon spathula) or spoonbill as they are often referred to due to their paddlelike snout, is a large and ancient fish that has survived relatively unchanged since the late cretaceous period around 68 million years ago when dinosaurs walked the earth. They can be found throughout North American in the Mississippi River Basin. While they are a protected and rare state threatened species in Ohio, they are found most commonly in Ohio River tributaries downstream of the first dams; particularly in the Scioto River south of Columbus (Rice and Zimmerman 2019). In Ohio, they can grow to a maximum size of 5′ and 184lbs, however fish ranging from 2-4′ and around 20-30lbs are much more common (Rice and Zimmerman 2019). The cause for their decline was attributed to increased turbidity, or suspended particles like clay and silt, and being cutoff from suitable spawning areas to reproduce due to the construction of dams (Rice and Zimmerman 2019). In order to understand why turbidity has impacted these fish so much and why their populations are beginning to rebound as water quality improvements t0 the rivers has been made, you must first understand how they feed.

Filter Feeding:

Despite their massive size and tough exterior, these fish are filter feeders that prey mostly on small plankton crustaceans, which are small organisms that float freely in the water. You may be wondering how it is possible for the paddlefish to eat enough of these organisms to grow to such a large size. Luckily for the paddlefish, they are excellent filter feeders like Humpback Whales. Having been described by early naturalists as “A living plankton net” these fish have hundreds of gill rakers that form a tight mesh that collects plankton as they swim around with their large gaping mouths open as seen in Figure 2.

Figure 2: Paddlefish gill rakers (Courtesy of John Lyons of Virigina Tech)

But what purpose does the paddle serve?

Electroreception:

The paddle or rostrum was once thought to have been used to dig through the stream substrate foraging for food, but research has proven that it is actually an electro sensory organ covered in sensory pores (Figure 3) used by the paddlefish to detect the weak electrical currents plankton give off (Wilkens and Hofmann 2007). In a study published in 2007, researchers ran feeding experiments on juvenile paddlefish where they placed the paddlefish in dark tanks and witnessed them able to seek out single small crustaceans that were placed in the tank (Wilkens and Hofmann 2007). They also noted that they would avoid metallic objects in the tank, even in the dark, as this likely interfered with their perception of electrical currents which may also hint at a further impact locks and dams could have on paddlefish by disrupting their ability to navigate rivers and access spawning habitat after dams were constructed (Wilkens and Hofmann 2007). If paddlefish can locate food even in the dark or muddy waters, then why has increased turbidity impacted them so much?

Figure 3: Paddlefish rostrum and closeup of electro sensory pores (Helfman et al. 2007)

Turbidity:

The issue with increased turbidity is largely due to their ability to finely filter feed. Some studies have shown that 50% of the gut content of some paddlefish was detritus (decomposing organic material like small leaves) and sand (Pyron et al 2019). Under highly turbid conditions, paddlefish gill rakers may become clogged with materials that are suspended in the water, making them unable to filter feed plankton effectively. In addition to not being able to filter feed as effectively, other studies have linked high turbidity to reduced growth of plankton species (Kirk and Gilbert 1990). Despite the paddlefish’s ability to find food solely using electroreception, they’d still struggle to find food as plankton growth can be reduced, leaving them less food in water with high turbidity.

Outlook:

At present, water quality in Ohio has been steadily improving after legislation like the Clean Water Act in 1972 and many fish species have since begun to bounce back after having been impacted by habitat and water quality degradation (Pyron et al 2019). As water quality continues to improve and many old and outdated dams are removed; granting these fish access to places to spawn, we can be hopeful that conservation efforts to protect this ancient Ohio fish will be successful and future paddlefish will be free to filter feed all they want.

 

Sources:

Helfman, G., Collette, B. B., Facey, D. E., & Bowen, B. W. (2009). The diversity of fishes: biology, evolution, and ecology. John Wiley & Sons.

Kirk, K. L., & Gilbert, J. J. (1990). Suspended clay and the population dynamics of planktonic rotifers and cladocerans. Ecology71(5), 1741-1755. Lon A. Wilkens, Michael H. Hofmann, The Paddlefish Rostrum as an Electrosensory Organ: A Novel Adaptation for Plankton Feeding, BioScience, Volume 57, Issue 5, May 2007, Pages 399–407.

Pyron, M., Mims, M. C., Minder, M. M., Shields, R. C., Chodkowski, N., & Artz, C. C. (2019). Long-term fish assemblages of the Ohio River: Altered trophic and life history strategies with hydrologic alterations and land use modifications. Plos one14(4), e0211848.

Rice, D. L., Zimmerman, B.. (2019). A naturalist’s guide to the fishes of Ohio. Ohio Biological Survey.