Reproductive effort of intertidal tropical seagrass as an indicator of habitat disturbance

Abstract

Habitat disturbance is one of the major causes of seagrass loss around the Andaman Sea in the Indian Ocean bioregion. Assessing the seagrass response to these disturbances is of utmost importance in planning effective conservation measures. Here we report about seagrass reproductive effort (RE) as an indicator to assess seagrass response to habitat disturbances. Quadrat sampling was used to collect seagrass samples at three locations (a disturbed and undisturbed site per location) of the Andaman and Nicobar Islands. The health of seagrass meadows was quantified based on density-biomass indices of the disturbed sites. A change ratio (D/U) was derived by contrasting the RE of disturbed (D) sites with the undisturbed (U) sites of all three locations. The relationship between RE and plant morphometrics were also quantified. Reproductive density of T. hemprichii was higher and significant at the three disturbed sites. The average reproductive density of T. hemprichii at the disturbed sites was 3.3-fold higher than the undisturbed sites. The reproductive density consisted around 52% of the total shoot density of T. hemprichii at the disturbed sites. In general, the increase in the plant RE was site-specific and was 4-fold higher at the three disturbed sites. Positive and significant correlations was observed between the change ratio of RE and the plant morphometrics, suggesting an active participation of seagrass morphometrics in the reproductive process. Increase in seagrass RE can contribute to the increase in population genetic diversity, meadow maintenance and various ecosystem functions under the influence of anthropogenic disturbance scenarios.