A Low-Cost Method of Measuring the In Situ Primary Productivity of Periphyton Communities of Lentic Waters

Summary

Presented here is a cost-effective and transportable method/facility for measuring the primary productivity of microbial mats under actual in situ environmental temperature and light conditions. The experimental setup is based on widely available materials and can be used under various conditions while offering the advantages of laboratory-based models.

Abstract

Measuring the in situ primary productivity of periphyton during the growing season gradient can elucidate the quantitative effect of environmental drivers (mainly phosphorus concentration and light intensity) and species composition on primary productivity. Primary productivity is mainly driven by light intensity, temperature, availability of nutrients, and distribution of the ionic species of the carbonate system in the respective depths of the euphotic zone. It is a complex system that is very difficult to simulate in the laboratory. This cheap, transportable, and easy-to-build floating barge allows measuring the primary productivity accurately-directly under the actual natural conditions. The methodology is based on measuring the primary productivity in real time using noninvasive oxygen sensors integrated into tightly sealed glass jars, enabling online oxygen flux monitoring and providing new insights into metabolic activities. Detailed seasonal in situ measurements of gross primary productivity of microbial mats (or other benthic organisms) can improve current knowledge of the processes controlling primary productivity dynamics in lentic waters.

Introduction

Primary productivity is the only entry of autochthonous carbon into the aquatic systems that form the entire system food web¹. Hence, the accurate estimation of primary productivity is an essential step toward understanding the functioning of aquatic ecosystems. Littoral zones are areas of high primary productivity and biodiversity. In addition to phytoplankton, periphyton (hereafter referred to as microbial mats) and macroalgae are assumed to significantly contribute to primary productivity in littoral zones². Due to their sessile lifestyle and significant spatial heterogeneity, quantification of primary productivity is....

Protocol

NOTE: Before sampling, determine the degree of replications based on the overall project needs, statistical design, or expected amount of sample variability.Five replicate pairs of light and dark incubation bottles are suggested for precise statistical analysis and to account for potential sample loss or breakage. The described floating experimental barge is designed to carry five replicates plus one pair of blank controls; see Figure 1 for a technical drawing of the experimental barge.

Results

Figure 5: Net and gross ecosystem productivity of microbial mats during daylight. (A) Light bottle-net ecosystem productivity: time course data of net oxygen productivity of microbial mats from the light bottles. The oxygen concentration change in incubation bottles was measured after 1 h during daylight. Grey circles: bottles with samples of m.......

Discussion

The methodology described in this paper is based on the principle of the light and dark bottle oxygen technique in combination with the noninvasive technique of measuring O₂ concentration using optical oxygen sensors. This system allows the parallel measurement of different incubation settings as the optical fiber for measuring O₂ can be moved quickly from bottle to bottle. The benthic communities from various depths can differ in taxonomic composition and productivity; simultaneously measuring them.......

Materials

Name	Company	Catalog Number	Comments
Aluminum angle L profile 40 x 40 mm x 3 mm, length 2,000 mm
Aluminum flat bar 40 x 3 x 350 mm
Bucket 15 L with concrete infill
Carabine hook with screw lock 50 x 5 mm
electric tape black
Extruded polystyrene (XPS) material 500 x 200 x 150 mm
Fibox 3 LCD trace	PreSens Precision Sensing GmbH		stand-alone fiber optic oxygen meter
Hondex PS-7 Portable Depth Sounder	Hondex  - Honda Electronics		to measures distances through water - to bottom depth measurement; https://www.honda-el.net/industry/ps-7e
KORKEN - glass tight-seal jar 0.5 L	IKEA		incubation bottles; https://www.ikea.com/cz/en/p/korken-jar-with-lid-clear-glass-70213545/
metal hook
Oxygen Sensor Spot SP-PSt3-NAU-D5	PreSens Precision Sensing GmbH		non-invasive optical oxygen sensor for measurements under Real Conditions
SCOUT infantable canoe	GUMOTEX		https://www.gumotexboats.com/en/scout-standard#0000-044667-021-13/11C
Screw 10 x 170 mm with hexagonal nuts
Screw 4 x 15 mm with hexagonal nuts
Screw 4 x 15 mm with wing nuts
Snap hooks 50 x 5 mm
Steel Carabine hook 50 x 5 mm
Steel chain with wire diameter 3 mm, inside link 5.5 x 26 mm
Steel chain, 5 m
toothbrush
tweezer
Washer 10 x 50 mm
Washer 4 x 10 mm
Washer 4 x 10 mm