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Delaware National Estuarine Research Reserve


      

  Archived Posts From: 2013

A day in the life of a horseshoe crab biologist

Written on: June 4th, 2013 in ResearchSt. Jones Reserve

Have you ever wondered what it might be like to be a horseshoe crab biologist? Well, I have the wonderful opportunity to be one!   A typical day begins at 8 am loading equipment at the St. Jones Reserve to a chorus of chirping birds and tree frogs.  What does a horseshoe crab biologist use?  We use plenty of small buckets for sediment samples, a couple ropes marked off at three meter intervals, some stakes painted orange, a clicker-counter, metal sediment slicer, and most important, a sediment core sampler!

Once at the beach, the sampling areas are established according to the high tide line and signs of horseshoe crab activity.  The marked ropes are set up to establish three meter by twenty meter transects.  Each biologist collects 20 five-cm deep sediment core samples randomly throughout each transect and places them into a bucket with a label with the date, beach name and transect designation.  This is repeated on 3-4 beaches a day.

The sample buckets are then brought back to the lab for processing.  The first step is to remove as much gravel, sand, and fine organic particles from the horseshoe crab eggs as possible.  This is done by emptying the sample bucket into a tall series of progressively finer wire-mesh sieves and using water to spray the eggs through the screen while separating out the rocks, shells and gravel.  If there is a large amount of gravel remaining in the egg sample (egg-size 1.6 mm), the sample is then run through a specially designed elutriation system (fondly referred to as Eggbert) which uses water to separate out the less dense eggs from the denser sediments.  Once the eggs have been separated out they are ready for counting!  If the number of eggs in the sample is small (< 4,000), the eggs are counted by hand.  If the number of eggs in the sample is large, there are counted volumetrically in a graduated cylinder.  The egg count data and location data is tracked for each beach each year and provides information regarding the availability of horseshoe crab eggs as a food source for migrating shorebirds. 

So, where is the fun?  Imagine walking onto a beach and seeing thousands of horseshoe crabs lining the shore, hunting for tagged crabs after sampling, photographing hundreds to thousands of shorebirds while they forage for eggs.  Like music?  Lab time offers a great opportunity to sing along to your favorite tunes while sieving samples and counting eggs!  Change the lyrics to a classic tune to create your own horseshoe crab theme song or collect shells, fossils and cool rocks from the sediment samples while sieving eggs.  Perhaps making bucket towers or cracking egg jokes while sifting and counting helps make the work more fun.  But most importantly, making lifelong friends while conducting important scientific work is the best benefit!  And, that is what it is like in a day in the life of a horseshoe crab biologist.  

By Amy Brossard


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