Exploring the seasonal dynamics within the benthic foraminiferal biocoenosis in a tropical monsoon-influenced coastal lagoon

Abstract

Benthic foraminiferal assemblages are widely used as bioproxies for coastal environment monitoring. The present study investigated seasonal variations in live benthic foraminiferal assemblages over a period of 12 mo from the largest coastal lagoon in Asia, which is strongly influenced by tropical monsoons. The investigation revealed an extremely low diversity of benthic foraminiferal assemblages, comprising 12 species, of which 8 were agglutinated. The most dominant taxa throughout the study period belonged to the genus Ammonia. The living assemblage was restricted to the topmost 4 cm of the sediment, with the majority of assemblages occurring in the top 2 cm. Data analysis revealed the presence of a significant variation in the biotic assemblage, indicating a patchy distribution. Overall, some of the benthic foraminiferal species, such as Ammomarginulina sp. and Miliammina obliqua, showed strong seasonal variation, while the dominant Ammonia spp. did not show any temporal variation. The environmental parameters displayed significant correlations with certain species, although no single factor could be identified as being the major force driving assemblage composition. The present findings of seasonality and correlations observed between certain factors with certain species may be utilized to improve biomonitoring in similar settings on a global scale. KEY WORDS:Benthic foraminifera · Coastal lagoon · Live assemblage · ANOSIM · UPGMA-based cluster · Ammonia OPEN PEN ACCESS CCESS

Understanding Impact of Seasonal Nutrient Influx on Sedimentary Organic Carbon and Its Relationship With Ammonia spp. in a Coastal Lagoon

“…populations are generally very abundant throughout the lagoon (Sen and Bhadury, 2016). Besides Ammonia populations, benthic foraminifera species diversity is low in this lagoon (in total 12 species) (Sen and Bhadury, 2016).…”

“…Previous reports have documented the presence of six different species of Ammonia (Rao et al, 2000) from the lagoon. However, based on more recent estimates and by incorporating taxonomic revisions Sen and Bhadury (2016) have only identified the presence of three species of Ammonia within the lagoon and their abundance is overwhelming but mostly restricted within the top 2 cm of benthic layer. It has been shown that there are three distinct morphotypes classified as Ammonia T2, T10 and T6 in Chilika lagoon (Sen and Bhadury, 2016).…”

“…However, based on more recent estimates and by incorporating taxonomic revisions Sen and Bhadury (2016) have only identified the presence of three species of Ammonia within the lagoon and their abundance is overwhelming but mostly restricted within the top 2 cm of benthic layer. It has been shown that there are three distinct morphotypes classified as Ammonia T2, T10 and T6 in Chilika lagoon (Sen and Bhadury, 2016). The nomenclature provided is to genetically separate with distinct morphological features (e.g., number of chambers in final whorl, absence of secondary calcite, pores having large diameter) observed in Ammonia T2, T10, and T6 (Sen and Bhadury, 2016) which are distinguishable from Ammonia tepida as established by Hayward et al (2004).…”

“…It has been shown that there are three distinct morphotypes classified as Ammonia T2, T10 and T6 in Chilika lagoon (Sen and Bhadury, 2016). The nomenclature provided is to genetically separate with distinct morphological features (e.g., number of chambers in final whorl, absence of secondary calcite, pores having large diameter) observed in Ammonia T2, T10, and T6 (Sen and Bhadury, 2016) which are distinguishable from Ammonia tepida as established by Hayward et al (2004). The Ammonia FIGURE 1 | (A) Location of the study area with respect to the Mahanadi basin, the major source of freshwater influx in the Chilika lagoon (B) location of the sampling stations with respect to the different rivers that flow into the lagoon and can act as potential point sources for pollution.…”

“…populations are generally very abundant throughout the lagoon (Sen and Bhadury, 2016). Besides Ammonia populations, benthic foraminifera species diversity is low in this lagoon (in total 12 species) (Sen and Bhadury, 2016). The lagoon is separated from the Bay of Bengal by a sand bar approximately 60 km long and lost its natural marine connection in 2001 due to siltation.…”