The Effects of Suspended Particulate Matter, Nutrient, and Salinity on the Growth of Amphidinium carterae Under Estuary Environmental Conditions

Abstract

The environmental conditions in estuaries display distinct variability along the river-ocean mixing continuum from turbid, eutrophic freshwater to clear, oligotrophic offshore oceanic water. In order to understand the effects of suspended particulate matter (SPM), nutrient, and salinity on phytoplankton growth, this study investigated the response of a harmful dinoflagellate (Amphidinium carterae Hulburt) to the ecological gradients in estuary environments. Rapid nutrient uptake and growth of A. carterae were detected in the nutrient-rich clear water, while nutrient concentration had little impact on the cellular chlorophyll a (Chl-a) content at the stationary phase. Light attenuation caused by SPM not only inhibited the specific growth rate of A. carterae but also prolonged its adaption period in turbid water, resulting in a delayed and weakened growth response. The elevated cellular Chl-a content under high SPM conditions resulting from photo-acclimation led to the decoupling of cell density and Chl-a concentration, indicating that Chl-a is not a reliable indicator for phytoplankton abundance in turbid environments. The combined effect of SPM and nutrient on specific growth rate of A. carterae can be explained by the comparative effect model, while the multiplicative effect model better predicted their interactive effect on the growth inhibitory rate (GIR). There is a transit of dominant limiting factor for phytoplankton growth along the salinity gradient in estuary environments. Salinity (for marine phytoplankton cannot survive under low salinity condition) and SPM are the dominant limiting factors at low salinities in nearshore turbid environments, while nutrient depletion exerts the dominant inhibitory effect in high salinity offshore water. Depending on the balance between enhancing nutrient limitation and reducing light limitation with increasing salinity, blooms most likely occur in the “optimal growth region” at intermediate salinities where light and nutrient are both suitable for phytoplankton growth.

Impact of Flash Flood Events on the Coastal Waters Around Madeira Island: The “Land Mass Effect”

“…For conservative nutrients, salinity can be used as a proxy to indicate the mixing processes affecting nutrient distribution (Liss, 1976). In dynamic environments, such as the ocean, many physical and biogeochemical processes including coastal upwelling, biological processes (e.g., nutrient uptake), remineralization, desorption, and adsorption of nutrients on settling particles (e.g., Carstensen et al, 2020;Jiang et al, 2021) cause relationships between salinity and nutrient concentrations to deviate from conservative behavior. Therefore, the use of salinity as a proxy for land-based nutrient inputs may not fully reflect nutrient distributions.…”

Evaluation of the Performance of Spline Interpolation Method in Mapping and Estimating the Total Suspended Solids over the Coastal Water of Pulau Tuba, Kedah

“…Suspended solids have also been blamed for damaging the fish gills and their visibility underwater [11]. High suspended particle also causes the marine and freshwater plant to get insufficient sunlight [12]. Due to this concern, an approach using spatial interpolation techniques can be used to monitor TSS in the aquatic ecosystem.…”

A Bayesian Approach to Carrying Capacity Estimate: The Case of Greek Coastal Cage Aquaculture

“…In particular, low salinities cause the increase of mortality of plankton species, depending on their salinity resistance [55]. Silicates (Si-SIO4) are major nutrients for siliceous primary producers (diatoms), which can become limiting factors in oligotrophic areas such as the Greek seas (similar to the rest of the Mediterranean Sea, with values starting from 1-3 μM in the west and reaching 0.003 μM in the Levantine basin) [56]. Most of the silicon inputs (up to 80% on a global scale) in the marine environment come from continental discharges, from both surface water (rivers mostly) and groundwater [56], though recently, it has been shown that beach weathering contributes to Si [57].…”

“…Demand for Si by primary producers is limited only to diatoms that require Si as much as N and P. A study in a Mediterranean coastal ecosystem showed that salinity affects the concentration of silicates, and in particular, high salinities correspond to low silicate concentrations [56]. This, combined with the high filtration of silicates along the sediments surrounding the underground discharges, results in a concentration of Si in the coastal waters which is less than 3.5% of the initial concentration in the groundwater (freshwater), and following a cycle of subterranean mixing, it can reach the inner shelf at even lower concentrations of 2.2% [56,60]. The Bayesian-CHAID model resulted in the inclusion of silicates in the group of important parameters, obviously due to its relation to salinity and its classification as a limiting factor, as well as since together with N and P, in the various forms that Salinity, together with temperature, has been reported that governs phytoplankton communities (hence chl-a and eutrophication), especially in diatom and cyanophytedominated communities [52].…”

“…Silicates (Si-SIO 4 ) are major nutrients for siliceous primary producers (diatoms), which can become limiting factors in oligotrophic areas such as the Greek seas (similar to the rest of the Mediterranean Sea, with values starting from 1-3 µM in the west and reaching 0.003 µM in the Levantine basin) [56]. Most of the silicon inputs (up to 80% on a global scale) in the marine environment come from continental discharges, from both surface water (rivers mostly) and groundwater [56], though recently, it has been shown that beach weathering contributes to Si [57]. Due to the reduction in the river outflows in the Mediterranean basin by 20% between 1960 and 2000, silicate concentration and availability have been reduced significantly [58].…”