Could marine animal conservation laws be responsible for the decline or extirpation of macroalgal populations in Bermuda over the past century?

Abstract

Using over 10,000 archival herbarium specimens from Bermuda, we compared the presence or absence of seaweeds from a century ago with our more than 5000 collections from the last 30 years. Populations of parrotfish, important herbivores of macroalgae in the tropics, have increased since the 1993 amendment to the Bermuda 1978 Fisheries (Protected Species) Order. A fish pot ban for Bermuda was put into effect in 1990 to protect a variety of fish including parrotfish and several species of grouper, important predators of parrotfish that were rarely seen in island waters at the time. Intertidal grazing West Indian top shells were reintroduced in 1982 to Bermuda, and since then, along with the rise in parrotfish populations, inshore populations of many macroalgae have dramatically changed. We suggest that several large and abundant Bermuda macroalgal species recorded in the early 20th century appear to have been extirpated or are greatly diminished in sizes of individuals as well as population abundance, and propose that marine animal protections over the past 35 years are a possible reason for the changes we are presently observing.

A revision of the genus Cryptonemia (Halymeniaceae, Rhodophyta) in Bermuda, western Atlantic Ocean, including five new species and C. bermudensis (Collins & M. Howe) comb. nov.

“…11; Kützing, 1869;Schneider & Searles, 1991). Specimens of Cryptonemia atrocostalis from North Carolina (Schneider & Searles, 1973, 1991 are considerably larger (to 2.5 cm wide and 25 cm tall) and more robust than the ones we have collected in Bermuda from 13-18 m over the last decade, perhaps due to the grazing pressure on Bermuda reefs, a phenomenon we have observed for several 'reduced forms' of macroalgal species in the islands (Schneider & Lane, 2008;Schneider & Flook, 2017). Howe (1918) reported island specimens that were approximately 10 cm tall, a bit larger than those that we have collected, the largest blades being 8 cm tall.…”

DNA sequencing and anatomy demonstrate that Pacific Codium simulans is a genetically variable species found in the floras of Bermuda and Florida

“…clavatum (Collins & Hervey ). Over the past quarter century, Schneider and Flook () monitored a persistent population of C. simulans in Walsingham Pond, a sheltered inland collapsed limestone sinkhole with underground connection to the sea, a population grazed by a solo resident green sea turtle where there are otherwise few herbivorous fish or invertebrates.…”