Provided by East River CREW (see page 111) Guide - archives/eee2c-lessons.pdf · Provided by East...

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�� Provided by Ocean Institute at Sandy Hook / Brookdale Community College (see

page 151 for contact information)

Reprinted with permission from The Ocean Institute at Sandy Hook 31

A Horseshoe Crab Primer

Some suggested activities for involving students. Dave Grant, Brookdale College’s Ocean Institute at Sandy Hook, NJ 07732

www.brookdalecc.edu/staff/sandyhook/index.html Research the literature on horseshoe crab history (Geological); biology; anatomy and physiology; Native American, Colonial, agricultural, research and medical exploitation.

Examine eggs, hatchlings and young horseshoe crabs (or sheds) to familiarize yourself with their anatomy.

Focusing on the various parts of a horseshoe crab shed, speculate on the use of each spine, leg, etc. to the crab (before observing live specimens).

Observe the behavior of horseshoe crabs in different wild or captive environments for swimming, burrowing and feeding activities.

Examine young (1-10 year old horseshoe crabs or sheds) and compare the presence of epibionts, scratches and other signs of wear-and-tear with older specimens (10+ year old). Create a chart or matrix to present your findings as a reference to estimate the age of crabs.

Develop a simple diagram or shell outlines (dorsal and ventral) to illustrate where various epibionts are concentrated on the shells of horseshoe crabs.

Develop a scientific (Phylogenetic) “Key of Species” found on horseshoe crabs. Use other features like epibiont attachment strategies, attachment sites, location in the food web or feeding behavior, to create a key of species.

Survey horseshoe crabs on nesting beaches and elsewhere to catalogue epibionts, frequency, and gauge the age spread of the population (See chart). Compare things like the horseshoe crab’s sex and numbers of epibionts present, or crab size and numbers present. Construct a graph to illustrate these factors.

Compare a number of horseshoe crabs and their epibionts and calculate average numbers of species and average area covered on a crab. Also compare the crab size and presence of epibionts. Develop a chart, graph or matrix to illustrate the relationship (If any) between these factors.

Develop a method to quickly survey a population of horseshoe crabs on a beach to calculate their sex ratio, species count of epibionts, and percent coverage by epibionts (data sheets, outline sketches to fill in data, etc.).

Start a collection of epibionts from horseshoe crabs or specimens from the beach. Most can be dried (mollusk and crab shells, bryozoans, worm tubes, egg cases) or pressed (algae). Soft tissue creatures (worms, hydrozoans) can be preserved in alcohol.

Compare the concentration and variety of invertebrates on a horseshoe crab with a similar sized rock or surface area of an inter-tidal piling. Which has more variety and biomass? Evaluate you data and speculate about any differences.

Research the ranges (Geographic, salinity tolerance, preferred habitat) of various epibiont species (and the horseshoe crab) to predict where these creatures may exist on horseshoe crabs. In areas where horseshoe crabs live outside the range of a particular epibiont, research similar species, or a species that fills a similar niche, to try to predict their presence on horseshoe crabs in that area.

Using pictures, observations, crafts materials or sheds, draw or construct models of horseshoe crabs and their epibionts. Make a horseshoe crab Origami model.

Create your own “SURVIVOR SHOW” game and place your team on an island where the most abundant resource is the horseshoe crab. Use horseshoe crab shells to make tools, musical instruments, games, etc.


Make plaster casts of tracks, footprints, and shell parts of horseshoe crabs in sand. Make a horseshoe crab paperweight.

Study the fossil history of horseshoe crabs and their current ranges around the world. Create a geological timeline for horseshoe crabs and emphasize their recent history with humans. Study the Latin origins of the scientific names of horseshoe crabs and their epibionts. Do these words describe the anatomy of the animals or habitat or some other feature? Search google.com and other Internet sources for information on horseshoe crabs, their value to humans, and their epibionts.

A Calendar of Sandy Hook (NJ) Horseshoe crab reports

Dates Location and behavior

January 1 A sluggish old male found at the tideline at the tip of Sandy Hook on the Annual New Years Day Beachwalk. Very unusual.

January-March Juveniles rarely found in sandy sediments in Horseshoe Cove marsh.

Early April Horseshoe crabs (Small, “clean” males and immatures) collected from crab traps off the beach in Long Branch, NJ 10-15’ of water.

Mid-April Horseshoe crabs stranded on the ocean beaches of Sandy Hook. High proportion of males with epibiont growth and damaged eyes.

Late-April Adults common in trawl nets in the bay.

May Peak spawning on Spring tides at sites like Horseshoe Cove. Individuals spotted as far upriver as Red Bank. Salinity 5-15 ppt.

June Lingering spawners. Great numbers of medium-sized exoskeletons on the beaches. Late June/ early July Hatchlings taken in plankton nets between Highlands and Oceanic bridges. August Shed exoskeletons of small, immature specimens common. September Last report of paired crabs at Horseshoe Cove

October Adults common in trawl nets in the bay. Occasionally snagged in 50-feet of water by fishermen in the Ambrose Ship Channel off Sandy Hook.

November-December

Horseshoe crabs taken in fish and crab trawls offshore on the continental shelf, and in the bay.

Aging Adult Horseshoe crabs – A subjective guide for mature adults that have shed 16-17 times in 9-10 years. (Adapted from Carl Shuster)

Age range Color, features, behavior Epibionts present

1-2 years as adults (11-12)

2-6 years as adults (12-16)

6+ years as adults (16-20)

Young Adults: Clean, firm and lustrous (Olive) carapace with few scratches or epibionts. Virgin males with atrophied second chela. Virgin females with pristine shell and no mating scars. Lively and vigorously try to escape when handled. Middle-aged Adults: Extensive scratches. Lustrous sheen wearing away and black layer becoming exposed. Epibionts usually present. Females have mating scars on the posterior shell pressure point areas and clasper scars on the trailing edge of the shell. Active. Old-Aged Adults: Carapace completely blackened with some areas worn down to a brownish layer, sometimes tinged with green. Shell is thin and easily depressed. Epibionts (5) usually common, and some can be large. Sluggish.


Epibionts on the H

orseshoe Crab – V

entral


Epibionts on the H

orseshoe Crab – D

orsal

�� Wetlands: Teacher’s Guide

Provided by Alley Pond Environmental Center (page 90)

Reprinted with permission from Alley Pond Environmental Center 36

6 Estuary Equilibrium

FOCUS: The human impact on the estuary ecosystem and ways to empower the students. OBJECTIVE: Students will explain the causes of problems in an estuary and propose some solutions . Can you help Pogo?! Background information Human activities seriously threaten wetlands especially estuaries and salt marshes. Pollution and industrial development harm the balance of nature and ecological integrity resulting in major loss of productivity and fertility. Some of these destructive activities include:

Construction: Channel dredging, dams, irrigation projects and harbor pilings change the overall abiotic and biotic features of these ecosystems.

Landfill and mining: Marshes are drained and filled in order to build airports, shopping centers, etc. and others are mined for sand, oil, and gravel which destroy their habitats. Sediments: Much sediment comes from construction, dredging, currents and erosion, and causes turbidity which affects photosynthesis. In the estuary, it smothers animals and chokes sediment feeders.

Chemicals: Wetland life is being poisoned by industrial waste, sewage, oil spills and pesticides. Fish and oysters that live in estuaries are unfit to eat because of the pollution which contains high concentrations of chemicals and pathogenic bacteria.

Excess nutrients: When nutrient levels are high in the water, algal blooms can result and this can cause depletion of oxygen. Then animals may die.

Hypoxia is a technical term for low levels of oxygen in the water caused by an over fertilization with nutrients, primarily nitrogen

Over harvesting of organisms and thermal pollution of the water can lead to a disruption of biological systems.

Point sources of pollution are pollutants discharged from an identifiable point, such as sewers, tunnels, pipes, ditches and channels

Nonpoint sources of pollution do not come from one specific location, but are discharges that are widespread overland runoff.

Many fish and shellfish suffer from the effects of this pollution and can not be taken and eaten by humans. The once famous Little Neck Clam in Little Neck Bay may not be harvested for consumption. A widespread devastating lobster kill occurred in Long Island Sound as a result of many of the above pollution problems.

Reprinted with permission from Alley Pond Environmental Center 37

Materials Notebooks, pictures, pens, stationery, testing equipment Motivator What problems can we find affecting wetlands? How can we help the marshes and the estuaries? Procedure � Research the various types of problems and issues associated with salt marshes and estuaries. Define point and non-point pollution and give examples found in your community. � Discuss the effects of industrial development and pollution on salt marsh and estuarine ecosystems. � Explain what regulations you would enforce if you were the manager of salt marshes and estuaries. Classroom Activities � Find out what governmental agencies are in charge of protecting wetlands like salt marshes and estuaries. Contact someone in this agency to come and speak to the class about its policies and laws protecting wetlands. During the discussion would you recommend any changes in these policies? Explain. � Select one salt marsh or estuarine invertebrate and describe its life cycle, feeding habits and adaptations to its environment. � Research what measures are in place to limit the quantity of phosphorus and nitrogen compounds being released into coastal waters. � Write letters to your city and state elected officials about protecting wetlands, marshes and estuaries. Give them 3-4 reasons why they are important.

Field Site Activities � Collect mud at low tide and examine small amounts of it under a microscope. Try to identify the organisms you observe and their roles in this environment. � Design and perform an experiment that tests the effects of different concentrations of salt on forest and salt marsh plants. � Measure the salinity and temperature along various locations in the estuary. Try to establish these testing stations at equal distances from an inlet to the bay or ocean. � Record your results and graph them. Discuss the significance of your data with your classmates.

�� “The Water Sourcebooks”

Provided by EPA (http://www.epa.gov/ogwdw000/kids/wsb/)

Reprinted from the Water Sourcebook 38

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