Water quality, ecological processes and management procedures in a periphyton biofiltration system in mariculture: A statistical analysis

Abstract

A periphyton biofiltration system of mariculture effluents was studied to identify ecological processes and management procedures that strongly affect the biofilter functioning, in order to attain optimal biomass production and nutrient removal. The multivariate statistical technique of factor analysis allowed reducing the large amount of data available into three main factors. The first factor, which accounted for 49% of the overall data variability, was herein called “biological activity” as it represents the joint effects on the variables measured of photosynthesis, N and P uptake, respiration and decomposition of organic matter. The second and third factors were “autotrophic biomass density” and “nitrite and phosphate uptake/release balance”, which, respectively, accounted for further 20% and 14% of the data variability. A conceptual model, describing the functioning of the periphyton biofilters, revealed a delicate equilibrium among the different processes, whose understanding help to manage the biofilters towards optimal production of periphytic biomass and nutrient removal. Raising flow rate raised the overall nutrient uptake rate but reduced uptake efficiency and diluted nitrifying particles. A reduced flow rate led to sedimentation of organic particles, decomposition and nutrients re‐mineralization. Apparently, control of water flow and nutrient content, periphyton substrate area and the cleaning of the effluent supply system are key management elements for the operation of a periphyton‐based biofilter system that maximizes both periphyton biomass production and nutrient removal.

Fishmeal replacement by periphyton reduces the fish in fish out ratio and alimentation cost in gilthead sea bream Sparus aurata

“…Samples of periphyton were used to determine levels of protein, lipids, carbohydrates, and ash in the dried biomass (Table 5 ) in order to prepare the experimental diets with periphyton as per these biochemical content results. The relatively high ash content in the periphyton, as well as in all feeds with a high level of periphyton, may be attributed to the relatively high diatom content in the periphyton biomass at this time of the year, based on our results from earlier studies on the community composition of marine periphyton and other studies conducted during the same time of the year 29 , 30 .…”

“…Marine periphyton from an IMTA biofilter system plays a valuable role in the removal of excess nitrogen and phosphorus from fishpond effluent and assimilating them into edible biomass for further use 44 – 46 . This is in addition to its other advantages in water oxygenation and pH balancing 29 , 47 . In earlier studies, periphyton in culture ponds reduced the amount of commercial aquafeeds required 36 , 42 , 46 but the potential of this edible biomass in replacing dietary fishmeal has not been reported until now.…”

“…The periphyton biofilter in this system was an octagonal pool with an effective working volume of 100 m 3 , alimented with the nutrient-rich fishpond effluent. The periphyton in this biofilter developed spontaneously on an artificial substrate of white plastic nets (mesh size 2.5 × 2.5 mm) following previous recommendations 29 , 30 . In order to culture the required biomass of periphyton within a single batch, the total substrate area in the biofilter was set at 215 m 2 , considering both sides of the net as effective surfaces for biomass development.…”

“…In recent years, marine periphyton has been identified for its potential in bio-conservation of waste nutrients in fishpond effluent, showing a simultaneous removal of both N-forms: ammonia and nitrate 22 , 27 . This is due to the co-existence of various organisms such as micro- and macro-algae, bacteria and other microorganisms in the periphyton mat 28 , 29 . Moreover, in contrast to the high aeration required in Ulva biofilters, marine periphyton can be cultured relatively cheaply in unaerated biofilters requiring only light and artificial substrate like plastic nets for development 30 , while the oxygen produced in the biofilters can be further used to support fish production in the primary culture ponds 27 , 31 .…”

Periphyton For Biofiltration And Fish Feeding in An Integrated Multi-Trophic Aquaculture System: A Case Study in The Gulf of Aqaba

“…Periphyton is an important food of invertebrates, tadpoles, and fish in their natural aquatic habitats [31]. In aquaculture, increase of primary production in the ponds is achieved by the addition of artificial substrate for periphyton development and fertilization with organic waste prior to introduction of fish.…”