Phytoneuston and Chemical Composition of Surface Microlayer of Urban Water Bodies

Józef Piotr Antonowicz,Anna Kozak

doi:10.3390/w12071904

Abstract

The concentration of chemical and biological parameters in the ecotone of the surface microlayer (SML) occurring between the hydrosphere and the atmosphere of urban water bodies was investigated. Parallel, sub-surface water (SUB) analyses were carried out to compare the SML properties with the water column. The concentrations of trace metals, macronutrients, nutrients, chlorophyll a, pheophytin, abundance and biomass of phytoplankton and the number of heterotrophic bacteria in both studied layers were analyzed. Each of the studied groups of chemical parameters was characterized by specific properties of accumulation. Trace metals occurring in concentrations below 1 ppm, such as Al, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Zn and metalloid As, were accumulated to a higher degree in SML than in SUB. Macroelement concentrations, with the exception of Mg, were lower in the SML compared to the SUB. Nutrients, autotrophic and heterotrophic microorganisms occurred in the SML to a higher degree than in the SUB. Bacillariophyceae dominated the analyzed water bodies, which are typical for the spring period, as well as Chrysophyceae, Chlorophyceae, Dinophyceae and Euglenophyceae. Cyanobacteria dominated in one of the ponds. The abundance of individual phytoplankton groups was significantly correlated with Ca, K, Na, P-org, SO42−, F−, Al and Sr.

Highlights

The surface microlayer (SML) is an ecotone, which constitutes an interface between the hydrosphere and the atmosphere
Water samples collected from the SML and subsurface water (SUB) were analyzed for a wide range of chemical elements, composition and abundance of phytoneuston and phytoplankton as well as counts of heterotrophic bacteria
Irrespective of the sampling station, nitrogen and phosphorus compounds were accumulated at a greater amount in the SML than in the SUB (EF from 1.40 to 4.38) (Figure 2 and Table 1)

Summary

Introduction

The surface microlayer (SML) is an ecotone, which constitutes an interface between the hydrosphere and the atmosphere. It is a thin layer of maximum 1000 μm in thickness [1]. The SML is capable of accumulating microorganisms and chemical substances at a rate as high as. The SML may accumulate toxic substances at greater amounts than observed in the pelagic zone [7]. It is the zone that accumulates nutrients [5,8] Such substances as calcium, magnesium, potassium or sodium, being macroelements found at high concentrations in the pelagic zone, are usually not accumulated in the SML [9]. The SML structure may be disturbed as a result of physical non-equilibrium processes such as temperature fluxes, irradiance, wind and wave action that influence

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