Salinity changes may influence dinoflagellate cyst morphometry: data from monsoon-influenced tropical coastal ecosystems

Abstract

Abstract Generally, dinoflagellate cyst morphology is species specific. Their variability due to environmental factors (temperature and salinity) makes them potential proxies for such factors. However, there is a dearth of information on the variability of cyst morphology from monsoon-influenced coastal ecosystems. This study on distribution and variability in the dinocyst morphometry of Pyrophacus steinii and Protoperidinium pentagonum from estuarine (Cochin port and Zuari estuary) and marine (New Mangalore port) ecosystems along the Indian west coast revealed that both are common and euryhaline species. However, variability in cyst morphometry was observed and correlated salinity values between the ecosystems. Other parameters (i.e. the prevalence of narrow temperature ranges and nutrient-rich conditions) may not be dominant in influencing cysts morphometry. Cyst length, breadth and processes length (only in P. steinii) of both were relatively larger and smaller at salinity ranges higher and lower than 25 psu, respectively. The data presented for different ecosystems are comparable in most parameters except salinity variations. This study extends the ranges of records for both species. Pyrophacus steinii cysts were significantly larger (up to 120 μm in Zuari estuary) than literature reports on cysts from higher salinity systems and salinity-related variability in P. pentagonum cyst size indicates notable potential proxy indicator of salinity.