Environmental Problems

Abstract

In many countries around the globe one of the environmental problems that are abundant in the marine estuaries are commonly caused by dinoflagellates. Researchers have discovered the pros and cons of these planktons and recorded so many harms they have created not only in the marine aquatic organisms but also in humans. This issue pertaining to the effects of dinoflagellates deserves more attention because it cannot be stopped for its bloom is a natural occurrence. But giving the overview of these planktons could give you readers about how you can possibly avoid being one of the victims of this ferocious microscopic alga. Even a single cyst of dinoflagellates can lead to harmful effects. This research will explain how these small organisms cause a huge depletion in fish and shellfish economy. Also, this will give you more information about its unique characteristics, abundance and how these tiny organisms can cause major problems in the environment. Having a background of these organisms can contribute to the future studies of how to control their blooms and avoid some untoward incident caused by dinoflagellates.

We all knew about Harmful Algal Blooms (HAB's) but the knowledge we have about these phenomenon is only little that we generally think that these are caused by alga. Little knowledge about HAB's is not enough to explain this kind of incident. Yes, these are caused by alga but the question behind this is what specifically is the kind of alga that are responsible for these change in coloration of the surface of the sea that cause a lot of troubles in living organisms? Who are responsible for these problems and who must be the one to be blame for causing this occurrence? Did these questions come into your mind?

What are Dinoflagellates?

Dinoflagellates are group of planktons. They are unicellular organisms that have a high role in the bodies of water as primary producers. They are classified as algae under the Phylum Phyrrophyta or commonly known as the "fire algae".

Dinoflagellates are an evolutionary ancient lineage that encompasses extremely diverse and abundant single-celled organisms. They are founded to be older than dinosaurs and just evolved before the base of eukaryotic evolution. They are said to have originated in the "Ediacaran Era" or earlier 570 million to one billion years ago. They were first discovered by Mῡller in 1773 and was later described by Ehrenberg in 1830's ("Dinoflagellates-Predators",n.d.). The dinoflagellates were first defined by Otto Bütschli in 1885 as the flagellate order Dinoflagellida. Botanists treated them as a division of algae, named it as Pyrrhophyta after the bioluminescent forms they undergo and also been called the Dinophyta or Dinoflagellata("Dinoflagellates",n.d.)

The word Dinoflagellate comes from the Greek word "dinos" which means whirling. The latter part of their name was derived from their distinctive characteristic which is the flagella they posses. Their size ranges from 2 micrometers to 2 millimeters (2µm-2mm).

Almost 2000 species of dinoflagellates are known and 90% of which are marine plankton, but they are common in fresh water habitats as well. They can be found in ocean, brackish water, beach sand, snow, as parasites in marine organism and as "symbionts in Coelenteratra and Radiolaria".

All dinoflagellates are surrounded by a complex covering called the amphiesma. In most

dinoflagellates, this covering is consists of cellulose plates referred to as "armor" while others are uncovered or referred to as "naked" . The thin cellulose plates in the pellicle are absent or few in unarmored dinoflagellates and they occur in multiple layers in armored dinoflagellates. The surface of armored ones consists of spines and other structures that protect them from predators. This also enables them to sink and increases the surface area for absorption of nutrients (Karleskint,Turner & Small,2006).

The distinctive characteristic that made them different from other planktons are their two unequal flagella. The simple flagellum lies in a horizontal groove encircling the cell called the "cingulum" that provides forward motion and spin while the other flagellum which is the longer one lies in a groove called the "sulcus" and trails behind providing some propulsive force, but acting mainly as a control for the movement ("Dinoflagellates", n.d.). They also possess three basic cell extensions namely: the lists, horns and the spines. Lists are a result of the theca having ridges. Horns are basically multiple forms of body elongation and the spines result from narrow thecal extensions. All three of the cell extensions increase surface area and volume but the true function of horns and spines is unknown ("Dinoflagellates", n.d.).

What are the survival strategies of Dinoflagellates?

In order to secure the survival of their group, dinoflagellates reproduce by means of "simple cell division". Most dinoflagellates are haploid and reproduce primarily by asexual cell division (mitosis). Sexual reproduction also occurs through fusion of two individuals to form a zygote that may remain mobile in typical dinoflagellate form or may form a resting cyst, which later undergoes meiosis to produce new haploid cells (cells that contain complete set of cells). Prof. Harold Monteclaro, UPV faculty and our former teacher in Aquatic Flora and Fauna (Fish101) said that cyst remains dormant for a period of time but even a single cyst dispersed in the ocean can latter cause blooms when they reach their active stage.

Also for survival they used "mixotrophic strategies" which means they supply their own food by "osmotrophy"(absorption of nutrients) or "phagotrophy" (engulfing nutrients).They have chlorophyll pigment called "peridin" that enables them to have a golden-brown color and they also store food as starch just like the plants. Many dinoflagellates are heterotrophs(animals that obtain carbon by feeding on the organic material present in other organisms, living or dead) and have evolved various mechanisms to ingest prey.Some are autotrophs(animals that made their own food) and many species are capable of both heterotrophy and photosynthesis (mixotrophic).

Are Dinoflagellates really harmful?

HAB's or Harmful Algal Blooms were formerly called "red tides" and are mainly caused by dinoflagellates when they form colony and undergo population explosion. The term "red tide" has