Is "specieal" an adjective for species?

More common in this instance would be to use species as a noun adjunct - maintain species diversity. There is a difference in usage between special (adj) and species (adjunct). And then there is the problem of confusion regarding the sense of special. See the quote below on regulations concerning species of special concern.

Increased Flexibility via Special Regulations Under Section 4(d) of the Act Section 4(d) of the Act allows the Service to implement special regulations that reduce or expand the normal protections for threatened species, if the Secretary of the Interior deems the special regulations are necessary and advisable to conserve the species. Such special regulations cannot be developed for endangered species. These special regulations may provide important flexibility to address species-human conflicts as the species approaches recovery and becomes more numerous and widespread.

That is from the USFWS. http://www.fws.gov/midwest/wolf/esastatus/e-vs-t.htm

I also had the same question. The answer I found most satisfactory for my context was "specific", justifying the phrase "trophic and specific marine ecosystems". You can check this Quora answer.