Bahia Junquillal

 Costa Rica

Marietta College Biology and Environmental Science Department Field Trip 2005/2007

Note: Lots of big, pretty pictures on this page - it may take a while to load, even over a high-speed connection!

Beach at Bahia Junquillal, Costa Rica

Bahia Junquillal - A last taste of Paradise

 

In 2005 we started in Santa Rosa, and when we went to the beach we headed down a rutted 4WD trail to a point near the beach and hiked the rest of the way.  We called it the death march, you can read about it here.

Eladio Castro

In 2007, Santa Rosa was the end of the trip, and we still wanted to see a Pacific Beach.  Our driver, Eladio, told us that with the start of the rainy season the path to the beach was impassible (even for him), and we couldn't go to Playa Nancite.  He recommended another beach; it was further away from Santa Rosa, but much more accessible.  So, we loaded into his vehicles and sent off to spend our last full (non-travelling) day in Costa Rica at the beach - Bahia Junquillal.

Sign, Beach at Bahia Junquillal, Costa Rica

Below, a Google Earth view of the area.  The field station at the site is near the number 1, and we hiked down the beach to the rocks at #2.  It's only about 1/2 mile between the two points, thus the main beach is about 1 mile long.

Google Earth view, Beach at Bahia Junquillal, Costa Rica

 

Beach at Bahia Junquillal, Costa Rica

The beach is a lovely site.  There is a park there, with picnic tables and another field station, but not much else.  Another group of people was there for part of the time we were there, but otherwise we had several kilometers of beach to ourselves.  Looking out to sea, you were hard-pressed to see any signs of human influence.

Beach at Bahia Junquillal, Costa Rica The beach is a long crescent bay bordered by tropical dry forest, here in the wet season.

At the southern extreme of the beach rock outcroppings reach the beach, interrupting the sandy beach.  Tide pools formed here provided another interesting place to explore.

Beach at Bahia Junquillal, Costa Rica

Beach at Bahia Junquillal, Costa Rica

The waters of the Pacific were living up to their name at this beach, which seems to be protected from the biggest waves.

The class walks down the beach doing some beachcombing on the way.

Class on beach at Bahia Junquillal, Costa Rica

Beach at Bahia Junquillal, Costa Rica

Even in the wet season the surrounding hills show their dry forest nature; the vegetation was nowhere near as lush as it was on the Caribbean beaches or at Manuel Antonio.
Sand sorted by the waves shows contributions of volcanic rock to the sands of the beach. Volcanic Sand - Beach at Bahia Junquillal, Costa Rica

Rocks, Beach at Bahia Junquillal, Costa Rica

The rocks here were as far as we went (memories of Nancite?).  In any event there were some tide pools here with a number of creatures to be found there.

Beach at Bahia Junquillal, Costa Rica

Ecology

Acanthocereus tetragonus, Beach at Bahia Junquillal, Costa Rica

Cacti would seem to be at home on a beach dune.  The dry sands - particularly on a beach in a tropical dry forest - is a water stressed habitat, and desert adaptations - reduction of leaves, photosynthetic stems, water storage, thick waxy cuticles, etc. all play an important role.

This cactus, Acanthocereus tetragonas, was on a dune just off the beach.

Acanthocereus tetragonus, Beach at Bahia Junquillal, Costa Rica

Avicennia germinans (Black Mangrove) , Beach at Bahia Junquillal, Costa Rica

Avicennia germinans (Black Mangrove) , Beach at Bahia Junquillal, Costa Rica

Rhizopora mangle (Red Mangrove) , Beach at Bahia Junquillal, Costa Rica

There were a few mangroves in the waterways behind the beach.  The mangroves here were not as extensive as those we had seen at Tamarindo (or Playa Nancite, for that matter), but there were two species present. 

Above, Black Mangroves (Avicennia germinans) grows near the water's edge.  Along with the flowers in the image at upper left, note the salt crystals on the surface of the leaves.  Several mangrove species get rid of excess salt this way.  With their roots extending down into salty water, the only way they can take in water is to take in salt water and thus they must get rid of the excess salt through such secretions.  It also takes a lot of energy to get water into the roots against the salt gradient; the energy is obtained by the roots burning the sugar produced in the leaves.  This in turn reaquires oxygen, but oxygen is hard to obtain in the bottom sediments, which are often anoxic.  The black mangroves solve this problem with pneumatophores, extensions on the roots which grow up to and above the surface of the ground and which have spongy tissue that helps conduct atmospheric oxygen down to the roots.

Left, the Red Mangrove, Rhizopora mangle, grows in a characteristic clump.  This species is recognized by its habit of growing in the water and its long, tangled aerial roots.

For more on Mangroves, Click Here.

Beach dunes at Bahia Junquillal, Costa Rica

Left:  A low beach dune being stabilized by the encroaching tropical dry forest.  Dunes exist in an intermediate stage of succession.  At times, the dunes have the advantage as storms bring in more sand and uproot vegetation; this causes dunes to build and move inland.  In more stable times, trees and other vegetation stabilize the dunes and the forest creeps to the seashore.

Right:  A view from the top of the dune looking down to the shore.  Any gap in the vegetation will allow sand from the beach to spill back into the forest.

Below left:  The forest ascendant; here vegetation is covering the sand and slowing the wind, thus keeping the sand in place.  

Below right:  one species that likes the sand is the ant lion, which constructs pits in the sand.  The unstable soil serves as a trap for small insects which tumble into the holes and cannot get purchase to get out (a fate promoted by the ant lion which tosses sand at the insect to get it to fall and to create small sandslides which bring the insect to the ant lion at the bottom of the pit.  There, the ant lion seizes the insect with long mandibles.

Beach dunes at Bahia Junquillal, Costa Rica

Beach dunes at Bahia Junquillal, Costa Rica

Ant Lions at Bahia Junquillal, Costa Rica

There were several species of crabs on the beach.  Right, a fiddler crab, with the characteristic mismatched claws on the beach.  Note the burrow nearby (probably from another, smaller crab) and the small balls of sediment.  The latter are created when a crab picks up a bunch of sand and rolls it around in its mouthparts, removing anything nutritious in the process.  The sand is then discarded in small balls.  Below right, the small balls of sand arranged in a radial pattern help locate a crab burrow.  The crab forages in all directions from this central point, and the castings from its feeding thus reveal the site of the burrow - at least until the next tide.  Below, a hermit crab from the rocks at the end of the beach.  Hermit crabs use the discarded shells of snails as a portable home.  Unlike the snail, the crab can't make the shell grow larger, so as the crab grows it must periodically cast off its current shell and find a slightly larger one.  Hermit crabs would be well-served by EBay.

Fiddler Crab  at Bahia Junquillal, Costa Rica

Hermit Crab at Bahia Junquillal, Costa Rica

Crab foraging at Bahia Junquillal, Costa Rica

Magnificent Frigatebird, Fregata magnificens, at Bahia Junquillal, Costa Rica

We saw a number of Magnificent Frigatebirds  soaring over the beach (along with pelicans and vultures).  In 2005, we also saw frigatebirds, but they were "Not aesthetically unpleasing frigatebirds" as opposed to "magnificent frigatebirds".

Snail eggs at Bahia Junquillal, Costa Rica

The trails and lumps you see in the image to the left were created by snails digging through the sand.  The shiny, gooey, transparent blobs they left behind are their eggs; I'm assuming the snails know what they are doing at that high tide will shortly sweep the eggs into the ocean; if the tide is falling the eggs would be stranded on the beach and no doubt vulnerable to drying out.

Snail eggs at Bahia Junquillal, Costa Rica

Snail eggs at Bahia Junquillal, Costa Rica

Spittlebugs at Bahia Junquillal, Costa Rica

Speaking or drying out, here is an insect that doesn't worry too much about it.  The spittlebugs (left) use their piercing mouthparts to tap into the sap of the plant, which they then whip into a froth.  The adults do this prior to laying eggs, and the nymphs (pictured) continue the effort.  With the "spittle" in place, the nymphs can feed protected visually by the froth, and perhaps chemically as well if the tree has any chemical defenses.  And, of course, the nymphs don't have to worry about drying out when they are covered in tree slime.

To the right you can see the spittlebugs undisturbed in a tree - but don't park your car under them when they are feeding!

Spittlebugs at Bahia Junquillal, Costa Rica

Termites at Bahia Junquillal, Costa Rica

Termites at Bahia Junquillal, Costa Rica

Above:  As usual, termites were common here.  The pictures above were taken after I broke through a few inches of the tube the termites had made connecting their aerial nest with the ground.  Within the tube, the termites were able to get easy access to the ground and keep predators away from the workers.  With the tube broken the parade of workers continued, but nasute soldiers (with the black heads) lined up facing outward to guard the workers.  This is seen even more clearly in the video below; several times ants approach the column but are driven off.  After a short time the workers will repair the tube.

Video of termites at Bahia Junquillal.

 

 

Pufferfish at Bahia Junquillal, Costa Rica

We caught a pufferfish in the water (yes, with out bare hands) and it obligingly puffed up, demonstrating its anti-predator defense.  The spikes are sharp, and on the inflated fish, really stiff.  We thought about playing catch with it, but that wouldn't have been much of a challenge, so we put it back in the water and let it swim off.

Tamarind (Tamarindus indica) at Bahia Junquillal, Costa Rica

Tamarind (Tamarindus indica) at Bahia Junquillal, Costa Rica

Fruit of the Tamarind

The tamarind tree, Tamarindus indica, is not a native of India (as its name suggests) but of Africa.  However, it was imported to India such a long time ago that the original describer, Linnaeus, was apparently fooled into thinking it originated there (even the common name, tamarind, alludes to an Indian origin.).  The fruit is very useful and the tree is planted extensively in India to harvest the fruit - a large tree can produce hundreds of pounds of fruit.  The pulp of the fruit is used in a variety of foods ranging from sauces and seasonings to confections and drinks (we drank it often in Costa Rica).  Substances obtained from the seeds can be used to stabilize ice cream and other products (giving them body).

A close look at the fruits, flowers and leaves of this tree will reveal its relationship to the bean family (Fabaceae).  You might note the similarities to the acacia trees and to locust trees as well.  This family is well-known for its symbiotic relationship with bacteria of the genus Rhizobium; the bacteria infect the roots of the plant and cause nodules to form.  In these nodules the bacteria are able to convert inorganic nitrogen to forms that the plants can use to make amino acids (and then proteins).  The bacteria get sugar (from photosynthesis) in return.  I was unable to find out for certain if tamarinds have these bacteria, but locust and acacia trees do; the bacteria allow them to live on soils that otherwise would not have enough nitrogen to support much plant life.

 

 

Learn more about tamarinds here.

Tamarind (Tamarindus indica) at Bahia Junquillal, Costa Rica

Chrysalis at Bahia Junquillal, Costa Rica

The leaf-like structure to the right is actually a butterfly chrysalis.  The caterpillar anchored itself to the bottom of a picnic table to make its transformation to an adult butterfly.

Ctenosaur (Ctenosaur similis)  at Bahia Junquillal, Costa Rica

Ctenosaur (Ctenosaur similis)  at Bahia Junquillal, Costa Rica

We got a lot of entertainment from this ctenosaur.  An iguana relative, ctenosaurs are fairly common at Santa Rosa, Playa Nancite, Bahia Junquillal, and Manuel Antonio.  This guy came up to us at lunch and seemed to be begging food, which we provided in the form of the papaya in the upper right photo here.  He also ate a lot of other stuff, but we won't go into that here.  I suppose it shouldn't surprise me; I have a number of turtles who have learned to associate humans with food.

Ctenosaur (Ctenosaur similis) with ticks at Bahia Junquillal, Costa Rica

Ctenosaur (Ctenosaur similis) with ticks at Bahia Junquillal, Costa Rica

The ctenosaur also gives us an excuse to talk about another form of symbiosis - parasitism.  In this case one of the symbionts, the tick, benefits; the relationship sucks for the ctenosuar.  This one had a number of ticks on its body; some are marked in the image to the left, and I'm sure you can spot them in the photo above as well.  The ticks penetrate the skin between the scales and drop off once they are engorged.

There are a lot of hymenoptera in the tropics and I'm always amazed at the diversity of the social wasps there, as compared to the temperate areas.  This wasp nest was built in the open, but  in a thorny tree, probably a protection against vertebrate predators who would love to get at the honey and protein-rich grubs inside - and who would be willing to take a few stings along the way.  At Santa Rosa we saw other wasp nests in acacia trees, where they are protected both by the thorns of the acacias and by the acacia ants.  Apparently the wasps smear a chemical deterrent on the branch where the nest is connected to the tree to keep the ants away from the nest. 

Wasp nest at Bahia Junquillal, Costa Rica

Tube Worms at Bahia Junquillal, Costa Rica

These Polychaete worms dig a U-shaped burrow in the mud of the mangrove swamp; while we were there we could watch the worms pumping water through their burrows.  This brings in oxygen and food, which the worms then filter from the water before it is expelled.  You can see it in the video below.

 

Video of worms at Bahia Junquillal.

Beach at Bahia Junquillal, Costa Rica

Being our last day "out in the wild" before we headed back to San Josť (and then to Ohio), we also took some time just to enjoy the beach.

Beach at Bahia Junquillal, Costa Rica

 

Return to Main Costa Rica Page