This is usually called a recession.
The New Economic Policy
Production
New York
The stock market does not lead or affect the economic but does tell you how the economic is doing. You might want to call it an index which tell you in advance if the companies in such economic are making improves or declines.
People who study marine biology are called marine biologists.
Marine biology and include (phycology, invertebate zoology, ichthylogy)
Zoology is the study of animals and botany, the stud of plants
A zoologist, zoology is the study of animals.
A zoologist.
The people that study ruins are archaeologist.
People who study pathology are called pathologists.
Zoologists.
Sedimentologists.
Hemographers
Zoologist
Physiologists