*** karachi is the largest city of pakistan and a hub of industrial activity. the coastal zone of karachi is extended up to 135 kilometers that is exposed to heavy pollution load of both domestic and industrial origin. likewise discharges of sewage and industrial effluent into aquatic and marine ecosystem is also on the rise. the organic load of sewage deplates oxygen levels in water and indirectly reduces the diversity of animals and plants life.
*** most of the coastal pollution is concentrated in karachi harbour where an estimated 90,000 tons of oil products from vessels and port terminals are dumped every year. extremely high levels of toxic heavy metals such as mercury have been documented, especially in the coastal waters and sea near karachi. these are likely to have both acute and chronic toxic impacts on human beings, marine biodiversity and fish-eating birds. the impacts of these pollutant on commercial fin-fish and shrimp fisheries are unknown, but are likely to be significant. *** Rehri creek is one of the neighbourhoods of bin qasim port and support a large community of fisherman. its stretches to 21.7 kilo meters in the south east of karachi coast, pakistan. its micro environment comprises of the coastal area of bin qasim district which includes the union council of rehri goth and ibrahim hydri besides the two settlements of chashma goth and laath basti.
*** Rehri creek is the heavily polluted area of karachi coast, where the effluents from korangi, landhi, karachi export processing zone, binqasim industrial area and pakistan steel mill are directly discharged into the sea. in addition to these the untreated waste water from metropolis of karachi and domestic effluents are from smaller coatal settlements is also released into the coastal water. the consequent contamination of fisheries and other fauna poses serious and potential health hazards.
*** The creeks area is dominated by mangroves that serve as a spawning and nursery ground for a number of commercially important marine fauna. the toxic pollutants from the rehri creek area reach to the mangrove areas. in addition, pollution from domestic, industrial effluents and cattle colony waste causes eutrophication and increases biomass in the form of algal bloom, which affects not only economically important marine fauna, but also affects mangrove seedlings. these algal blooms grow profusely and inhibit the growth of mangrove seedlings that results in mortality of mangroves on a large scale.