In regard to the estuary conservation strategy involving the removal of contaminated substrate, which of these statements are true? select all that apply. a it is one of the least expensive strategies for conserving estuaries. b it disturbs the biotic factors of the estuary floor. c it reduces contamination of the water and substrate of the estuary.

B. It disturbs the biotic factors of the estuary floor.

C.  It reduces contamination of the water and substrate of the estuary.

Estuary is a partly enclosed water body which receives water from the streams of rivers and sea. An estuary is a wetland where freshwater river streams meets the ocean water. Therefore, estuary exhibit accumulation of  brackish water.

Sedimentation of bed of estuary is caused when the rain, rivers and streams wash off the sediments from the land into the estuary. The sedimentation is speed up by the pollutants being discharged by the agricultural and industrial waste. The accumulation of sediments disturbs the aquatic life and if the sedimentation exceeds, the water in the estuary will dry and estuary will be converted into dryland.

The removal of sediments or contaminated substrate from the estuary can disturb the biotic factors as this measure will remove the plants already growing on the substrate. This may kill the aquatic animals as they may also come out of water along with the substrate.

The removal of contaminated substrate will reduce the contamination of the water. This will help in retaining the aesthetic quality of the region as water will appear clear rather dirty. It will also help to maintain the biodiversity of the estuary water as pollution free water will promote the growth of aquatic plants and animals.

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.