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Open Access | Published: 2021 - Issue 1

EFFECT OF ENVIRONMENTAL FACTORS ON CHRYSOCHROMULINA GROWTH; THE MOST COMMON CAUSE OF FISH MORTALITY IN JEDDAH

Ftoon Ashour1*, Fotoon Sayegh1-3

 

  1. Department of Biology, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia.
  2. Marine Natural Products Research Unit, King Fahd Medical Research Centre, King Abdul Aziz University, Saudi Arabia.
  3. Environmental -Deputy, Saudi Ministry of Environment Water and Agriculture (MEWA).

ABSTRACT

A phytoplankton bloom, dominated by the prymnesiophyte Chrysochromulina sp., developed in two areas of the red sea coast, Al-Nawras and Al-Arbaeen lagoons (Jeddah, Saudi Arabia) in the fall of October and December 2016. Chrysochromulina sp. dominated at total cell densities of average 3×106 cells.ml-1, and have caused variable degrees of mortality in fish. Fish gills were examined under a microscope and showed the presence of Chrysochromulina sp cells. This study was conducted to investigate environmental factors that affect the growth characters as a function of different salinity, pH, temperature, and light-regime (light duration and intensity). Light-regime showed the highest effect among all the factors tested, at 10:14h L:D for the light duration with a growth rate of (0.352 μ.d-1), dry weight of (1552.601 ng), production per dry weight of (542.613 ng.d-1), and chlorophyll-a content (0.221µg.ml-1), as for light intensity, the best results were at around 60 to 70 µmol with a growth rate of (0.426 μ.d-1), dry weight of (2213.086 ng), production per dry weight of (929.419 ng.d-1), and chlorophyll-a content of (0.205 µg.ml-1). Other factors were best at 15°C, 40 PSU, and 7 to 8 for the temperature, salinity, and pH, respectively. No acute toxicity was present. Therefore, the fish mortality was most likely related to the morphological aspect of the isolated species by clogging of fish gills accompanied with suitable environmental conditions, grazing and a very low dissolved oxygen level in both lagoons

Keywords: Chrysochromulina, Fish Mortality, Haptophyta, Harmful Algae, Prymnesiophyte, Nanoplankton cell


Introduction

On Wednesday 12/ October, fall of 2016, a bloom of Chrysochromulina sp. occurred along the coast of Al-Nawras lagoon in Jeddah city, Saudi Arabia. The bloom killed thousands of sardine fish that entered the bay at the time and suffocated. Another bloom happened on Friday 2/ December 2016, along the coast of Al-Arbaeen lagoon in Jeddah city, Saudi Arabia. It also killed larger fish (milkfish and Tilapia) and some crabs. The Prymnesiophyta or Haptophyta are a group of uninucleate flagellates characterized by the presence of a haptonema between two smooth flagella. The prymnesiophyte genus Chrysochromulina presently embraces about 60 formally described species [1]. Chrysochromulina species have been found to make up 45 to 73.5 % of the identified species, and 2.5 to 50 % of the total number of nanoplankton cells [2]. Blooms threaten the environmental or public health and the fast development of economy, industry, and social life is one of the factors affecting negatively the environment. Sewage input into the coastal areas is the major problem along the coast of Saudi Arabia [3]. Jeddah is a major coastal city that has a network to collect municipal wastewater [4]. Some HABs are harmful by virtue of their sheer biomass, whereas some are capable of producing toxins. Other species are non-toxic to humans but harmful to fish and invertebrates (especially in intensive aquaculture systems) by damaging or clogging their gills [5, 6]. The aim of this study was to investigate several environmental factors in order to reveal possible effective factors in growth and bloom formation (Figure 1).

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