Welcome to our blog.

This space is devoted to sharing information about Point Reyes and the surrounding areas. Find information about the local plants, wildlife, the hiking/biking trails around Point Reyes National Seashore, tales of our recent outings and explorations, wildlife encounters & sightings, and other exciting happenings in the natural world.

Monday, July 9, 2012

Drakes Estero


The mouth of Drakes Estero as seen from Schooner Bay
Photo by Casey Newman, 2011, All Rights Reserved
It’s July, which means that Drakes Estero is open for boaters again! Drakes Estero is a 160-acre estuary in the heart of Point Reyes National Seashore, and its pristine waters teem with wildlife. Kayak tours of Drakes Estero launch from Schooner Bay and spend the day paddling through eelgrass and oyster beds, and over muddy and sandy bottoms where many invertebrates make their homes. These shallow, protected waters still rise and fall with the tides, so paddling the Estero can be tricky, and paddling times have to be carefully scheduled so that we can launch and land without wading through too much nutrient-rich (read: stinky) mud.

A young bat ray attempts to blend in with the sand
Photo by Casey Newman, 2011, All Rights Reserved.
An estuary is a protected body of water formed where freshwater from rivers and streams mixes with salt water from the ocean. Drakes Estero has several streams that drain into it, and it is protected by a sandbar that stretches across most of the mouth of the estuary. The brackish water formed by the mix of fresh and salt waters, along with the warmer temperatures, creates and ideal mix for conditions that are sheltered and rich in nutrients, building a prolific food web that supports many types of animals in the water and on the land.

Double Crested Cormorants drying off in the morning sun on the Estero
Photo by Casey Newman, 2011, All Rights Reserved.
Named for Sir Francis Drake, Drakes Estero is one of the possible sites where he landed in 1579 to repair his ship. Many other creatures call this water their home, including rock and kelp crabs, many species of fish, clams, limpets, and barnacles. Leopard sharks and bat rays cruise through the Estero to feed, mate, and give birth. Buffleheads, loons, and scoters come into the Estero to feed on fish eggs that attached to the eelgrass. Both brown and white pelicans will summer here, and double crested cormorants live here year round.

A group of harbor seals hauled out on a sand bar
Photo by Casey Newman, 2011, All Rights Reserved.
  
The largest colony of harbor seals in the Seashore makes its home near the mouth of Drakes Estero. Harbor seals give birth to their pups usually between March and June, and nurse the pups for three to six weeks. During that time, the pups are learning how to fend for themselves, and the waters of Drakes Estero are perfect for that. Each year, the Estero closes between March 1 and July 1 so that the seals are not disturbed by the presence of humans. Once the Estero reopens, curious harbor seal pups are seen in the area, but they are well on their way to their adult size of 5 to 6 feet and 200 to 300 pounds.
 
If you would like to join us on a tour of Drakes Estero, check out Exploring Drakes Estero for more information and tour dates. This trip is often a day full of wonder, and also of paddling, so be sure to check out the clothing recommendations and call or email us with any questions!

Monday, July 2, 2012

Bioluminescence, Part 2


Bioluminescence is produced by a chemical reaction similar to the one that happens when a glow stick is broken. This reaction releases energy as light. The color of the light that is produced is usually blue or green, but can be red, yellow, or orange, depending on the chemicals used in the reaction. Most animals produce only one color of light, but some fish and worms use two colors of light

Looking for fish beneath cliffs of Laird's Sandstone on Tomales Bay
Photo by Casey Newman, 2011, All Rights Reserved.


Some animals, like fish and shrimp, use photophores, or special organs to produce light. Others, such as jellyfish, have specialized cells scattered over their bodies that glow. Certain species of organisms play host to bioluminescent bacteria, which produce light in exchange for room and board. There are some species of squid that produce bioluminescent ink, which is squirted out as a defense mechanism.  Single celled organisms such as bacteria and dinoflagellates use special compartments in their cell to separate the chemicals that react to produce light, combining the compartments when necessary.

At depths of between 200m and 1000m in the ocean, up to 90% of animals use bioluminescence to blend in with their surroundings. The light that reaches down into those depths is blue-green, and these animals will use bioluminescent photophores (cells or organs that produce light) to match the amount of blue-green light around them, camouflaging themselves.  Other fish that live at those depths produce red light. Many organisms that live that deeply cannot see red light, so the fish that produce it can use the light to see their prey without being seen.  Deeper in the ocean, where conditions are always cold and dark, animals do not need bioluminescence to blend in, but they do use it to attract prey and for communication and courtship. These animals have unique patters of photophores, which may help them to recognize others of their species.

Plainfin Midshipman Fish
Photo copyright Terrence J Fidler, 2006,robots4farms.com
One type of bioluminescent fish, called the plainfin midshipman fish, lives deep in the Pacific Ocean but migrates to the coast in the summer to lay their eggs. These fish are a type of toadfish with no spots or stripes on their dorsal fin. Their photophores are arranged in a U-shape on the underside of their body, and the photophores look like the buttons on a naval officer’s uniform, which is how they get the name midshipman fish. The photophores are used to blend in with the light around them while they are in the ocean, which keeps predators from seeing them from below.

The male midshipman fish returns to Tomales Bay first, digging out a nest in the rocks along the shoreline. The rocks at Nick’s Cove are a favorite spot for these nests. Once there, the males begin to hum to attract females. The hearing of the female midshipman fish is so accurate that they can tell the difference between each male’s hum and find the nest of the hum they like best. Once there, the female will lay her eggs and return to the open ocean. The males fertilize and take care of the eggs, continuing to hum until their nests are full of eggs from many females. The males guard the nest until the eggs hatch and the hatchlings are ready to be on their own.

To hear the plainfin midshipman fish’s hum, visit Discovery of Sound in the Sea: http://www.dosits.org/audio/fishes/plainfinmidshipman/.