Preliminary assessment of spatial and short-term variability of bio-optical properties in a tidal dominated estuary (Bahía Blanca, Argentina).

ARENA, MAXIMILIANO; DELGADO, ANA L.; CELLERI, CARLA; PRATOLONGO, PAULA D.

Regional Studies in Marine Science

ELSEVIER

Año: 2019 vol. 29 p. 1 - 11

2352-4855

Estuarine environments are very complex systems whose productivity is defined by multiple biological andphysicochemical interactions. Thus, monitoring the biophysical properties of estuarine waters becomes fundamental toour understanding of their ecosystem functions. Remote sensing retrieval of biochemical and biological variablesappears as a complementary tool, providing information at a high spatial and temporal resolution and thus allowing usto study processes that cannot be comprehended based only on in situ data. However, the quality of remotely senseddata strongly depends on ground-truthing, using discrete in situ measurements. The aim of this study was to describetemporal (short term) and spatial (across short distances) variations of optically active water components in the BahiaBlanca Estuary (BBE, Argentina), and to characterize their relationship with bio-optical properties. Concentrations ofsuspended particulate matter (SPM) and chlorophyll-a (Chl-a), as well as the absorption by colored dissolved organicmatter (acdom (443)), considered as a proxy of the concentration of colored dissolved organic matter, were tightlycoupled to tidal forcing, causing significant short-term variations. Along the estuary, a steep gradient was observedwith higher concentrations through the head of the channel. Considering bio-optical properties, absorption by non-algalparticles (anap (443)) dominates the absorption budget of these optically complex waters, followed by absorption byphytoplankton (aph (443). aph (443) was closely related to variations in Chl-a, but anap (443) showed increasedvalues under the influence of sewage discharge. Considering in situ measurements of water reflectance, a high shortterm variability was observed in response to tidal forcing, as well as large differences across relatively short distances.For the first time in the BBE, bio-optical properties of seawater were quantified, and their variations described atdifferent scales. These results revealed a highly variable environment from the optical perspective and have largeimplications for the validation of remote sensing products.