Crayfish as Bioindicators for Environmental Health in Freshwater Ecosystems
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Heavy metal toxicity, how crayfish absorb it, and its implications in environmental health.
Heavy metal toxicity, how crayfish absorb it, and its implications in environmental health.
• ───── Table of Contents ───── •
• ───── Table of Contents ───── •
• ───── Before we begin... ───── •
• ───── Before we begin... ───── •
What exactly is a bioindicator?
What exactly is a bioindicator?
A bioindicator is any living organism, such as a plant, microbe, or animal, that can be used to assess the health of the ecosystem in which they are found.
In other words, they are used for assessing environmental health and biogeographic changes taking place in the environment.
What is heavy metal toxicity?
What is heavy metal toxicity?
Heavy metals are naturally occurring elements that can be found in at least small amounts throughout the earth. Depending on how much accumulates or is exposed to the environment, it can become toxic. In an area where the concentration of heavy metals like lead, mercury, cadmium, arsenic, chromium, etc. is high, it can pose a significant threat to the health of living organisms, including humans, plants, and animals. This is because of the potential harmful effects when ingested or absorbed through the skin, or inhaled via the respiratory system.
• ───── A Little Introduction ───── •
• ───── A Little Introduction ───── •
Image courtesy of: https://www.astacology.org/AboutCrayfish.asp?uid=Guest
Meet the Crayfish!
Meet the Crayfish!
This crustacean goes by many names, Crayfish, Crawfish, Crawdad, even Mudbug! They are a small invertebrate mainly found in freshwater streams and ponds. You can typically find them underneath rocks and debris. They will eat a variety of things found in freshwater environments, including other crawfish.
Found in your own backyard!
Found in your own backyard!
There are 14 species of Crawfish found in the state of Maryland, 5 of which are not native. Of those 5 species, 3 of them are considered invasive by the Maryland Department of Natural Resources. Pictured to the right is one of the most invasive species, the Virile Crayfish.
You can find them throughout the state in almost any freshwater stream. The Maryland DNR uses them as a bioindicator macroinvertebrate during their annual Stream Survey.
Click below to see all of the native and invasive species found in Maryland.
↓↓↓
An invasive Virile Crayfish found in Herbert Run, on the UMBC campus. Collected by Mary Clare McDonough.
• ──── Heavy Metals and Crawfish ──── •
• ──── Heavy Metals and Crawfish ──── •
Diagram courtesy of: Mitra, Saikat, et al. "Impact of heavy metals on the environment and human health: Novel therapeutic insights to counter the toxicity." Journal of King Saud University-Science 34.3 (2022): 101865.
How do heavy metals accumulate in freshwater?
How do heavy metals accumulate in freshwater?
Heavy metals can accumulate in freshwater through a variety of ways. Some of the major sources of heavy metal pollution is mining, agricultural runoff, and municipal or industrial wastewater. These pollutants can affect the water itself, its inhabitants, the soil, and the surrounding flora/fauna. Organisms that live in the affected water can absorb the metals, which hurt them and any larger organisms that may consume them. The metals can also absorb and bind to the sediment, either in or around the water, which harm organisms and fauna that grow or feed on it.
Which heavy metals are typically tested for?
Which heavy metals are typically tested for?
Some of the metals usually seen in polluted waters are:
Cadmium (Cd)
Copper (Cu)
Zinc (Zn)
Lead (Pb)
Arsenic (As)
Chromium (Cr)
Nickel (Ni)
Internal anatomy of a crayfish, courtesy of: https://bioclass.cos.ncsu.edu/bio402_315/arthropods/new%20arthropod/16%20sys%20summer.html
How are they absorbed by Crayfish?
How are they absorbed by Crayfish?
Heavy metals will accumulate in the hepatopancreas, antennal gland, gills, and exoskeleton tissues. The major structure in this list, the hepatopancreas, is an active organ in the detoxification process for the crawfish.
it acts like a liver or pancreas in humans, filtering and digesting for the animal
the building up of heavy metals in crawfish is known as bioaccumulation
Metals can be measured in the crawfish via tissue analysis. This can be accomplished through a variety of techniques like tissue staining and microscopy, mass spectrometry, etc.
• ───── The Moment of Truth ───── •
• ───── The Moment of Truth ───── •
But ... are they good bioindicators?
But ... are they good bioindicators?
Evidence of metal absorption in crawfish has larger implications for their surrounding environment and ecosystem health. Now for the big reveal....
•───★ Click here for the answer! ★───•
•───★ Click here for the answer! ★───•
⋆ ·˚ ༘ * Short answer...Yes they are! ⋆ ·˚ ༘ *
More Specifically...
More Specifically...
When analyzed from heavily polluted water sources, crawfish tissues, on average, had more accumulation of the heavy metals also found in the sediments of their environment. If the crawfish were affected by toxic metals, that indicated a larger issue regarding their environment's health including other organisms that may consume them. This makes them a bioindicator!
In other words, if they have too much heavy metal, then so does the sediment and other animals in the environment.
This has implications in how to approach future pollution control strategies, assessments of contamination, and food safety testing especially in areas with a heavy commercial need for crawfish.
• ───── Beyond Bioindication ───── •
• ───── Beyond Bioindication ───── •
Environmental Health and Human Health Implications of Heavy Metal Toxicity
Environmental Health and Human Health Implications of Heavy Metal Toxicity
Environmental Health
Environmental Health
While metals can be found naturally throughout the earth, a buildup of too many or too much can lead to major problems for the environment. Toxic metals seep into the earth and affect much of their surroundings. Additionally, they remain for a longer because they cannot be broken down naturally. Prolonged exposure can be dangerous to an ecosystem, creating an almost continuous cycle of contamination.
Cadmium → highly toxic in most amounts, accumulates in the water, soil, and plants of ecosystems which causes significant damage
Zinc → essential and harmless in smaller amounts but environmental exposure to large amounts through mining or industrial activities can create toxic effects on the surrounding environment
Copper → this is an essential metal for many plants and organisms but the accumulation of too much can cause toxicity
Lead → usually found in small amounts naturally, but large amounts can be found through human activities like manufacturing, mining, and fossil fuel burning; highly toxic to humans and ecosystems alike in large amounts
Arsenic → non-essential metal that poses a risk to the environment due to the fact that it is exceedingly poisonous to plants, organisms, etc.
Chromium → extremely dangerous and carcinogenic, interconversion between its two naturally stable states is highly toxic
Nickel → naturally abundant but can create adverse reactions due to prolonged emissions
Human Health
Human Health
Human consumption of crawfish can be indirectly toxic depending on the level of pollution in its environment. Additionally, if the animal lives in a highly polluted ecosystem, it has implications for the overall health of any organisms that live in the surrounding vicinity.
Cadmium → it is a human carcinogen that can damage the kidneys, liver, heart, bones, and respiratory system, it can also interfere with brain development in children
Zinc → can be healthy in small amounts, but if too much is ingested it can cause stomach problems such as vomiting and cramps
Copper → can be digested by the body in small amounts, but can be dangerous if the body is unable to process correctly
Lead → can cause a variety of health issues, including kidney, cardiovascular, neurological, and bone disease; children are at higher risk of lead poisoning
Arsenic → highly dangerous to humans and can cause cancer and even skin lesions, incredibly poisonous
Chromium → large amounts or prolonged ingestion can lead to intense stomach problems, fever, and liver/renal problems, extremely toxic and considered carcinogenic
Nickel → low amounts are harmless generally but prolonged exposure can cause allergies, nasal/lung cancer, and kidney and cardiovascular diseases
The bottom line is...
The bottom line is...
𓆝 𓆟 Thank your local bioindicators! 𓆝 𓆟
𓆝 𓆟 Thank your local bioindicators! 𓆝 𓆟
Scientists can use bioindicators to assess the health of an ecosystem and any initial signs of environmental degradation usually before any drastic damage. Without organisms like crawfish, there would be no measurable way to determine the extent of pollutants in ecosystems, and therefore no way to determine how healthy (or unhealthy) their environment is. They play a massive role in the fight to prevent pollution and its long-term effects.
• ───── Fun Stuff! ───── •
• ───── Fun Stuff! ───── •
･ ｡ﾟ☆ Click on the crayfish for some fun facts! ☆ﾟ.
･ ｡ﾟ☆ Click on the crayfish for some fun facts! ☆ﾟ.
⇩
⭒ Fun Fact #1 ⭒
⭒ Fun Fact #1 ⭒
Missouri has seven crayfish species that occur nowhere else in the world!
⭒ Fun Fact #2 ⭒
⭒ Fun Fact #2 ⭒
The long pincered crayfish (Orconectes longidigitus) can grow over six inches long.
⭒ Fun Fact #3 ⭒
⭒ Fun Fact #3 ⭒
A quarter pound of crawfish contains 82 calories!
-ˏˋ Make your own Crawfish! ˊˎ-
This is an easy and cute origami tutorial to make a crayfish! While he may not be the best bioindicator compared to the real deal, he makes an excellent friend for your desk or bookshelf!
• ───── References ───── •
• ───── References ───── •
Primary
Primary
Alcorlo, Paloma, et al. "The use of the red swamp crayfish (Procambarus clarkii, Girard) as indicator of the bioavailability of heavy metals in environmental monitoring in the River Guadiamar (SW, Spain)." Science of the Total Environment 366.1 (2006): 380-390.
Allert, Ann L., et al. "Effects of mining-derived metals on riffle-dwelling crayfish in southwestern Missouri and southeastern Kansas, USA." Archives of environmental contamination and toxicology 63 (2012): 563-573.
Allert, Ann L., et al. "Ecological effects of lead mining on Ozark streams: in-situ toxicity to woodland crayfish (Orconectes hylas)." Ecotoxicology and Environmental Safety 72.4 (2009): 1207-1219.
Anderson, Mary Bitner, et al. "Metal accumulation in crayfish, Procambarus clarkii, exposed to a petroleum-contaminated bayou in Louisiana." Ecotoxicology and Environmental Safety 37.3 (1997): 267-272.
Antón, Alvaro, et al. "The use of two species of crayfish as environmental quality sentinels: the relationship between heavy metal content, cell and tissue biomarkers and physico-chemical characteristics of the environment." Science of the Total Environment 247.2-3 (2000): 239-251.
Secondary
Secondary
Citations colored green indicate blog or news posts.
“Investigating Stream Health with the Maryland Biological Stream Survey.” Natural Resources News, news.maryland.gov/dnr/2023/11/02/investigating-stream-health-with-the-maryland-biological-stream-survey/. Accessed 20 Nov. 2024.
Arriaza, Ana. “Stream Critters - Acuminate Crayfish.” My Green Montgomery, 10 Aug. 2021, mygreenmontgomery.org/2021/species-of-interest-stream-critters-acuminate-crayfish/.
Goretti, Enzo, et al. "Heavy metals bioaccumulation in selected tissues of red swamp crayfish: An easy tool for monitoring environmental contamination levels." Science of the Total Environment 559 (2016): 339-346.
Mitra, Saikat, et al. "Impact of heavy metals on the environment and human health: Novel therapeutic insights to counter the toxicity." Journal of King Saud University-Science 34.3 (2022): 101865.
By: Mary Clare McDonough, Aya Malinovsky, Claudia Lopez Gonzales
By: Mary Clare McDonough, Aya Malinovsky, Claudia Lopez Gonzales
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