Find out more about the Hudson’s amazing animals and the challenges they face from climate change.

• Horseshoe Crab
• Mollusks
• Forbes Sea Star
• Atlantic Purple Sea Urchin
• Hermit Crab

One way that scientists study how animal populations change is by tagging them to track their movement. Help out by letting the U.S. Fish & Wildlife Service know when you see a tagged horseshoe crab.

Horseshoe Crab

Fun Facts:

• Horseshoe crabs aren’t actually crabs. They’re more closely related to spiders and scorpions.
• They’ve existed for 450 million years, since before dinosaurs and trees.
• They have 10 eyes: 2 big compound eyes like an insect, 2 simple eyes that see shapes but not detail, and 6 photoreceptors that see light and shadow.
• They usually move by walking, but when they swim, they often do a backstroke.
• Their blood is blue because they use copper to carry oxygen in their blood, instead of iron, like humans do.

Climate Connection: Sea-Level Rise:

• Horseshoe crabs lay their eggs on beaches along the estuary. Sea-level rise submerges some of these sandy areas, leaving horseshoe crabs fewer places to spawn.
• Horseshoe crab eggs and young also face other climate risks. Hotter temperatures and intense storms can reduce survival rates.
• If horseshoe crabs suffer, so do species that depend on them. For example, Rufa Red Knot (Calidris canutus rufa) shorebirds rely on eating horseshoe crab eggs in Delaware Bay during a stopover on their yearly 9,000-mile migration.
• To learn more about how horseshoe crab populations and habitats are changing, and how to better protect them, ecologists and volunteers visit local beaches and do counts of crabs and eggs.
• Horseshoe crab counts in some areas of the estuary are holding steady so far, while in others, like Jamaica Bay, populations have been declining over the past decade.
• Interested in helping out with a horseshoe crab count? Find monitoring sites in New York and New Jersey.

Mollusks (Channeled Whelk, Knobbed Whelk, Quahog) & Ocean Acidification:

Fun Facts:

• The knobbed whelk is the state shell of New Jersey.
• Whelks grow their own shells (unlike hermit crabs, who scavenge theirs).
• Whelks look kind of like the better-known conch, but whelks live in cold water and are carnivorous, while conchs live in tropical water and eat plants.
• You can estimate the age of a quahog by counting the rings on its shell, like with a tree. The oldest recorded Northern quahog was at least 106 years old.
• The tongue-like thing sticking out of a quahog shell is actually its foot.
• Quahogs can move about one to two inches in 15 minutes.

Climate Connection: Ocean Acidification:

• Mollusks need carbonate in seawater to build the hard shells that protect their soft bodies. A process called ocean acidification is reducing the amount of carbonate (CO₃²⁻) available to them, which means their shells can become thin and brittle.
• Ocean acidification is related to the same greenhouse gases that cause climate change. The oceans absorb some of the excess carbon dioxide that we release into the atmosphere when we burn fossil fuels, and this changes the oceans’ chemistry.

Forbes Sea Star

Fun Facts:

• Forbes sea stars eat by expelling their stomach out their mouth, wrapping it around prey, and digesting their food outside of their body.
• They have a photoreceptor (like an eye that senses light and dark) on the end of each of their five arms.
• They can regrow their limbs after an injury.
• They have hundreds of tube-like feet that they move by pumping water through them, like a mini hydraulic system.

Climate Connection: Warming Waters:

• Higher water temperatures are linked with diseases that can harm or kill sea stars, including sea star wasting disease.
• Forbes sea stars also seem to be expanding their range as waters warm, moving north into areas that were previously too cold for them.
• Beyond sea stars, higher temperatures displace marine animals of many kinds. In general, marine species are moving 5-10 times faster than land species. Eventually, they’ll run out of places to go

Atlantic Purple Sea Urchin

Fun Facts:

• Don’t worry, the spines of the Atlantic purple sea urchin aren’t venomous or poisonous.
• They walk using both their spines and shorter tube feet that stick out all around their spherical bodies.
• Sea urchins and sea stars both belong to the phylum of echinoderms, which means “spiny skinned”.
• Sometimes they put empty clamshells on their heads for protection, like a hat.

Climate Connection: Warming Waters:

• Sea urchins are relatives of sea stars. Like their relatives, they’re likely to experience some negative effects from warming waters, though perhaps to a lesser extent than sensitive sea stars. Research suggests that higher temperatures reduce urchins’ ability to reproduce.

Hermit Crabs

Fun Facts:

• Hermit crabs don’t grow their own shells. They move into an empty shell left by a deceased sea snail, and when they outgrow it, they go house-hunting for a new one.
• Sometimes they steal shells from each other.
• They have one large claw for defense and one small claw for eating and sealing off their shell.
• They pee out of their “face”, near the base of their antennae.

Climate Connection: Ongoing Research:

• Scientists are investigating how climate change affects hermit crabs’ ability to find good shells to move into. Not only will ocean acidification will make available shells weaker, but higher temperatures seem to create stressful conditions that lead to hermit crabs choosing shells that are too small or too large

Find Out More

• Find out which Northeast fish and shellfish species are most affected by climate change using NOAA Fisheries’ Climate Vulnerability Assessment Tool.
• See the in-depth research behind NOAA climate assessments for the Horseshoe Crab, Channeled Whelk, Knobbed Whelk, Northern Quahog, and Maine’s climate assessment for the Forbes Sea Star.