Phytoplankton fuel the energy flow from zooplankton to small nekton in turbid mangrove waters

Abstract

Fish, zooplankton, seston, benthic microalgae and mangrove leaves were examined to investigate the trophic role of zooplankton in the food web of Matang estuaries. Despite the high turbidity and large amounts of detrital material in the water column, the study reveals that phytoplankton fuel the energy flow to zooplankton and small nekton in mangrove-fringed estuaries. The stable carbon isotope (δ 13 C) values and C/N ratios (7.2 to 8.2) of fine seston (< 63 µm) in estuaries indicate the importance of phytoplankton (δ 13 C: −22.8 ± 0.6 ‰) to zooplankton (−23.4 to −18.2 ‰) nutrition, with a trophic contribution of 70 to 84%, whereas mangroves contributed <11%. In adjacent coastal waters, zooplankton (−19.2 to −15.1 ‰) grazed on both phytoplankton and benthic diatoms (−17.3 ± 1.24 ‰). Aggregated or mucilage-secreting diatoms (giving depleted δ 13 C values) were abundant in the estuarine seston, but did not appear to be consumed or assimilated by zooplankton. Stomach content analysis showed significant consumption of zooplankton, especially copepods (mainly Pseudodiaptomus annandalei), sergestids (Acetes spp.) and mysids by young and small nekton (<14 cm standard length) in mangrove estuaries, while δ 13C values indicate the increasing importance of mangrove carbon to juvenile fish nutrition (8 to 44%). The range of δ 15 N values from primary producers to small predatory fish indicates 4 trophic levels (excluding true piscivores) in Matang estuaries, with zooplankton at the second and third trophic level. KEY WORDS: Stable isotopes · Stomach contents · Phytoplankton · Zooplankton · Nekton · Turbid mangrove watersResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 469: 7-24, 2012 shrimps, constituted a large proportion of the diet of young juvenile and small-sized fishes (Chew et al. 2007, Then 2008, Tanaka et al. 2011.As mangrove detritus constitutes a large proportion of the organic matter in mangrove estuaries, there is a general perception that the estuarine food web is fueled by mangrove leaf carbon processed by both benthic micro-and macro-organisms (Odum & Heald 1975, Werry & Lee 2005. However, the trophic pathway from mangrove detritus to higher consumers (particularly fishes) has become a contentious issue based on the recent findings from stable isotope studies (e.g. Fleming et al. 1990, Marguillier et al. 1997, Bouillon et al. 2000. Indeed, alluded to phytoplankton and microphytobenthos providing substantially more energy than mangrove detritus to consumers in open mangrove waterways. Although several experimental and field observations have indicated ingestion and assimilation of vascular plant detritus by zooplankton (DeMott 1988, McKinnon & Klumpp 1998 and juvenile decapods (Newell et al. 1995, Dittel et al. 2000, Schwamborn et al. 2006, these studies also indicate that, given the choice, they would prefer live food.Senescent mangrove leaf litter may be unattractive as food to most animals because it is nutritionally poor (high C/N ratio), not...

Migratory Pattern of the Spotted Scat (<i>Scatophagus argus</i>) in the Mangrove Estuary of the Matang Mangrove Forest Reserve, Malaysia, Estimated by Stable Isotope Analysis

“…In the three smallest specimens (13.0-15.0 mm TL) analyzed here, the characteristics of the tholichthys larval stage (i.e., protective sheath-like bony plates covering the head) still remained. Chew et al (2012) estimated that 8-44% of nutrition for juvenile fish in the Matang Mangrove Forest Reserve (MMFR) is derived from mangrove sources, with mangrove-derived carbon occurring in the upper estuary becoming more important. In the present study, the δ 15 N values of Scatophagus argus collected from the river and creek areas (S1/R2-R6, SLG2 and C1-C4) were more enriched (5-7‰) than those of phytoplankton in coastal waters, microphytobenthos (R2, R5 and C3), and mangrove leaves in the estuary (Fig.…”

Temperature-and sex-specific grazing rate of a tropical copepod Pseudodiaptomus annandalei to food availability: Implications for live feed in aquaculture

“…This is because, compared to rotifers or Artemia , copepods have a higher nutritional value (Drillet, Jorgensen, Sorensen, Ramlov, & Hansen, ; Evjemo, Reitan, & Olsen, ; Rasdi & Qin, ; Rayner, Hwang, & Hansen, ), a wider range of size variation in nauplii, copepodites and adults (Golez, Takahashi, Ishimaru, & Ohno, ) that can fit to different larval fish, and their zic‐zac swimming behaviour that make them more attractive to fish larvae (Ajiboye, Yakubu, Adams, Olaji, & Nwogu, ; Støttrup, ; Støttrup & McEvoy, ; Støttrup & Norsker, ). Among copepods, the calanoid Pseudodiaptomus annandalei is highly abundant in tropical and subtropical coastal ecosystems and in aquaculture ponds in the Indo‐Pacific region (Blanda et al, ; Chew, Chong, Tanaka, & Sasekumar, ; Dhanker, Kumar, & Hwang, ; Hwang et al, ). The density of P. annandalei in aquaculture ponds may be higher than 300 individuals per litre (Blanda et al, ).…”

Trophic niche partitioning of dominant North‐Atlantic krill species, Meganyctiphanes norvegica, Thysanoessa inermis, and T. raschii

“…Where λ is the TL of the baseline used, i.e., TL = 1 for POM, δ 15 N consumer = δ 15 N of krill, δ 15 N base = δ 15 N of POM for each sampling date and Δ n is the estimated trophic discrimination factor for nitrogen. As trophic discrimination factors are undefined for krill and might be subject to uncertainty because of variability of the trophic discrimination factor with diet quality (Caut et al ), species (Philips et al ), season (Dionne et al ) and/or metabolic rate (McCutchan et al ), a trophic discrimination factor of 2‰ for nitrogen was chosen based on McCutchan et al () and Chew et al ().…”