why would plaque be found in the sea?

Answer 1

As far as I know, plaque is only found within living organisms...not in the sea...perhaps your are referring to something similar???

The word plaque or placque may mean:

Dental plaque, a yellowish film that builds up on the teeth
Atheromatous plaque, a buildup of fatty deposits within the wall of a blood vessel
Mucoid plaque, a supposed thick coating of abnormal mucous material in the colon
Commemorative plaque, a flat ornamental plate or tablet fixed to a wall, used to mark a significant event, person, etc.
Viral plaque, a visible structure formed by virus propagation within a cell culture
Amyloid plaque, an extracellular protein buildup implicated in various diseases (Alzheimer's disease, Parkinson's disease).
Plaque or placque may also refer to:

Plaque, a (usually) small, disk-shaped growth, common in some forms of skin cancer
Pleural plaque is a term for pleural fibrosis, often caused by exposure to asbestos

Answer 2

where there is life there are excesses like plagues ,at least for a while,untill Nature balances things out again