Phosphorus as a driver of nitrogen limitation and sustained eutrophic conditions in Bolinao and Anda, Philippines, a mariculture-impacted tropical coastal area

Abstract

The dynamics of nitrogen (N) and phosphorus (P) was studied in mariculture areas around Bolinao and Anda, Philippines to examine its possible link to recurring algal blooms, hypoxia and fish kills. They occur despite regulation on number of fish farm structures in Bolinao to improve water quality after 2002, following a massive fish kill in the area. Based on spatiotemporal surveys, coastal waters remained eutrophic a decade after imposing regulation, primarily due to decomposition of uneaten and undigested feeds, and fish excretions. Relative to Redfield ratio (16), these materials are enriched in P, resulting in low N/P ratios (~6.6) of regenerated nutrients. Dissolved inorganic P (DIP) in the water reached 4μM during the dry season, likely exacerbated by increase in fish farm structures in Anda. DIP enrichment created an N-limited condition that is highly susceptible to sporadic algal blooms whenever N is supplied from freshwater during the wet season.

Periphyton characteristics influence the growth and survival of Holothuria scabra early juveniles in an ocean nursery system

“…During these trials, N:P ratios were consistently lower than the Redfield ratio (16). This shows that regenerated nutrients were enriched in P, presumed to be from detrital organic matter from fish farms (Ferrera et al, ), which are near this study site. In addition, a high volume of mud‐like deposits was found in the hapa nets in Trial 4, which indicates that periphyton may have been light limited, constraining the growth of the autotrophs.…”

“…The first and second 30 days following the net change during each trial are hereafter referred to as cycle 1 and cycle 2 respectively. Ten‐day averages of chl‐ a and N:P ratios in the water column for cycles 1 and 2 were acquired from the CCMS equipped with sensors (Ferrera et al, ), located ~6 km from the experimental site. Average temperature and rainfall data for the respective experimental periods were acquired from the Tropical Rainfall Measuring Mission (TRMM) satellite website for Bolinao, Pangasinan.…”

“…The northeast monsoon peaks from January to February, while the southeast monsoon peaks in August (Cinco et al, ). Additionally, Bolinao, the site of this study, is located near a mariculture area established in the 1970s, where nitrogen‐limited and eutrophic conditions have persisted, and harmful algal blooms (HABs) with fish kills have recurred since 2002 (Azanza, Fukuyo, Yap, & Takayama, ; Ferrera et al, ; San Diego‐McGlone, Azanza, Villanoy, & Jacinto, ). The objective of this study was to investigate the biofilm and environmental characteristics that affect the growth and survival of juvenile H. scabra reared in floating hapas .…”

Phosphorus release from coastal sediments: Impacts of the oxidation-reduction potential and sulfide

“…Under some conditions, benthic sediment may act as an important P source for the overlying water (Sondergaard et al, 1999), and even create N-limited condition (Ferrera et al, 2016). P exchange processes between the sediment and overlying water are known to be affected by physico-chemical conditions and biological processes, which can also influence the existing forms of P (Qian et al, 2011;Pan et al, 2013).…”

Behavior and development of larvae in the sponge Haliclona amboinensis

“…The sites both experience strong wave action during the monsoon seasons and have an annual mean temperature of 29.7 ± 0.3°C and mean light intensity of 7,137 ± 1,505 lux. Fish farm effluent and submarine groundwater discharge contribute to elevated nutrient concentrations at the sites (Cantarero, Blanco, Cardenas, Nadaoka, & Siringan, 2019; Ferrera et al., 2016; Quimpo et al., 2020; Senal et al., 2011).…”