Biodiversity Differences in Freshwater and Estuarine Ecosystems


There are very few references on the biodiversity in freshwater and estuarine ecosystems of tropical countries. Students in tropical regions, therefore, cannot appreciate the differences between these two ecosystems in their own locality. Most of the published literature is descriptions of freshwater and estuarine ecosystems in temperate regions.

In recognition of this information gap, this article summarizes the two ecosystems and contains links to detailed descriptions of freshwater and estuarine ecosystems in Puerto Princesa, Palawan, Philippines. Palawan is well-known as a haven of wildlife and rich ecosystems from mountains to the sea.

This article characterizes only a portion of these highly diverse ecosystem found in Palawan particularly a representative freshwater and an estuarine ecosystem.

Why the Dearth of Literature on Freshwater and Estuarine Ecosystems?

Information on freshwater and estuarine ecosystems of tropical regions is lacking. It may be due to the lack of regard to the critical role these ecosystems play in people’s lives in communities or cities. It may also be due to the inability of educators in many tropical countries to develop and publish material in tune with their local settings.

Many of the local teachers still adhere to their traditional modes of teaching. They occupy themselves with classwork and regular lecture sessions, restricted by their four-cornered classrooms. Or probably, they have devoted themselves to economic activities to keep up with the ever-growing prices of goods and services.

Whatever the reason, many students in tropical countries learn from the books published by authors in other places, which may not apply to their specific location. There should be a change in paradigm among teachers.

Recognizing this, I always engage my environmental science and marine biology students in fieldwork as I teach subjects that require them to go to the field and explore the environment. It may be a Dynamics of Ecosystems course or the subject Research 01, where they need to familiarize themselves with actual research situations, i.e., in the field.

I always attempt not to teach them, but to mentor them along the way. Let them discover, so to speak.

Field Trip to Freshwater and Estuarine Ecosystems

There were two separate occasions of fieldwork that I undertook with my students to get familiar with these ecosystems. These are:

1) a trip to the freshwater ecosystem of Balsahan by graduate students enrolled in the Dynamics of Ecosystems course, and

2) a trip to the estuarine portion of Iwahig River.

Both ecosystems exist in the City of Puerto Princesa. It would take about 15 minutes to get to these ecosystems and explore the resources found therein.

Freshwater Ecosystem of Balsahan

We discovered a very diverse array of wildlife in the upper freshwater portion of the Balsahan River. Among these is a species of Insulamon,  a crab endemic (or only found) to Palawan.

Insulamon sp., a freshwater crab endemic in Palawan.
Insulamon sp. found in Balsahan river.

We surveyed in 2010, but then references on proper identification of the crab are not available, so we could not identify it correctly. No taxonomist was also available for consultation. What we lack in taxonomic skills we compensate by taking a photo of the crab for future reference.

Eventually, Dr. Hendrik Freitag, animal ecologist of Ateneo de Manila University, identified the crab as Insulamon palawanense in 2012. It was featured in the National Geographic Online Magazine. Dr. Freitag happened to visit Palawan State University where I teach and saw the picture in one of my online articles. He confirmed the crab indeed belongs to the same species he discovered.

We also saw a small, almost inconspicuous leaf frog, even an endemic species, hiding under the leaves along the riparian zone of Balsahan River. This funny-looking frog has skin that protrudes like horns on its head.

You can find the complete report in late post I wrote based on the original in the following post:

Estuarine Ecosystem of Iwahig River

Researchers have not well studied estuarine ecosystems in tropical regions, especially in the unique Island of Palawan, which has wildlife species that show more affinity with nearby Borneo Island than the rest of the Philippines. Experts attribute this similarity to land bridges that connect mainland Palawan with Borneo.

Despite the itchy bites of the sandfly (local name: niknik), marine biology students braved the waist-deep waters near the Iwahig River’s mouth. Many species of wildlife were photographed and then released back into the water. Likewise, we identified the mangroves growing in the estuarine portion of the river.

Notable among the animals is another crab of purple color. Is it another Insulamon? We don’t know because no information on a crab with such an appearance is available. Proper identification requires a considerable number of crabs, some measurements, and a lot of descriptions filled with jargon. The picture says it all, anyway.

The trip lasted only for about two hours, but we collected a diverse collection of photographs on the biodiversity of the estuarine ecosystem. This collection is better than any book published in printed format.

I will update this article as I make revisions to the articles published on this site.

Stay tuned.

© 2012 October 27 P. A. Regoniel | Updated 18 February 2024