Sea Otter Heroes: The Predators That Saved an Ecosystem
As he continued his graduate studies Brent focused on one specific intertidal area called Elkhorn Slough pronounced slew an inlet of Monterey Bay in Northern California The long narrow slough is an estuary where freshwater from nearby creeks and rivers mixes with salt water from the ocean Pelicans harbor seals and sea otters thrive Thick meadows of seagrass grow among the sand and rocks below the surface The twisting slough borders the farms of the Salinas Valley which grow acres and acres of strawberries artichokes brussels sprouts lettuce celery tomatoes spinach and broccoli Known as America’s Salad Bowl the valley produces most of the United States salad greens Many of these fields are only steps from the water and they have a direct effect on the health of the slough Elkhorn Slough is one of the most nutrient polluted estuaries on the planet Brent says Sea otters sleep eat and groom while floating at the water’s surface Pickers with large bags strapped to their backs harvest vegetables on a Salinas Valley farm 6
Farmers spray chemical fertilizers on crops Farmers spray chemical fertilizers on crops to help them grow strong and fight off to help them grow strong and fight off disease Then rain and regular watering rinses disease Then rain and regular watering rinses the fertilizer off the plants and into nearby streams rivers and eventually the ocean This runoff contaminates the waterways with extremely high levels of nutrients which can disrupt the balance of marine ecosystems the plants and animals in a habitat Brent discovered that Elkhorn Slough didn’t react like most nutrient-polluted waters Usually the excess nutrients encourage large amounts of algae to grow The algae coat each blade of seagrass and prevent the grass from performing photosynthesis Without photosynthesis the seagrass can’t grow and reproduce so it dies And because of the important roles seagrass plays in the environment our air quality coastlines and fishing industry suffer But the seagrass in the slough was healthy and lush and green Brent says It didn’t make sense but it was fascinating This seagrass thrived and in theory it should not In Elkhorn Slough seagrass floats just below the surface of the water The healthy bright green color surprised Brent Why did the seagrass flourish Brent was determined to find out But his journey to discovery would zigzag like the slough itself requiring crafty detective work the scientific method and a smidgen of luck 7
CHAPTER 1 THE MYSTERY UNFOLDS TO BRENT THE HISTORY OF THE SLOUGH IS AS FASCINATING AS ITS SEAGRASS MYSTERY About eighteen thousand years ago a glacier carved out the slough’s channel When the glacier retreated or melted salt water surged in to take its place Freshwater from nearby rivers also flowed in bringing sediment with it bits of sand and rock that settled on the estuary floor These sediments eventually formed the muddy banks of the salt marshes that border the slough The Elkhorn Slough was part of a vast tidal network of estuaries in the Salinas River valley Brent says It used to be massive Over the last two hundred years as the area became more settled the size of 8
the slough shrank Southern Pacific Railroad laid tracks in 1872 that separated eastern portions of the slough from the saltwater tides From the 1880s to the 1940s farmers and ranchers dried out land for fields and pastures by digging ditches and building dikes to hold back the tides In 1908 a winter storm with strong waves moved huge amounts of sediment and closed the mouth of the Salinas River north of the slough The same storm opened a new mouth a short distance south causing the river to bypass Elkhorn Slough That eliminated the slough’s largest source of freshwater And in 1946 the US Army Corps of Engineers dredged an area next to the Pacific Ocean to form Moss Landing Harbor Each of these events changed the slough’s size its shape or the ratio of freshwater to salt water The present-day slough is only 7 miles 11 km long San Francisco San Francisco San Francisco San Francisco San Francisco San Francisco San Francisco San Francisco San Francisco San Francisco San Francisco San 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Francisco Bay Santa Cruz Santa Cruz CALIFORNIA CALIFORNIA CALIFORNIA Elkhorn Slough GREAT BASIN DESERT Kirby Park Monterey PACIFIC OCEAN Bay Elkhorn Slough Main channel bay Salt flats Monterey Carmel Salinas Salinas River River River River Valley Valley Valley Valley Seal Bend Monterey Bay Moss Landing P A C I F I C O C E A N 0 0 5 1 Mile 0 0 5 1 Kilometer N 0 0 Miles 25 50 25 Kilometers 50 75 Los Angeles Elkhorn Slough extends inland from Monterey Bay and includes a main channel as well as shallow marshy salt flats 9
