Monitoring spatio-temporal variation in molluscan grazing pressure in seasonal, tropical rock pools

Wai, Tak-Cheung; Williams, Gray A.

doi:10.1007/s00227-006-0291-7

Cited by 14 publications

(16 citation statements)

References 27 publications

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“…Some though attain escapes such as on heterogeneous substrata and in cracks and crevices as well as pools; Ulva and other several foliose species were seen growing luxuriantly in pools and low on the shore as the season changes into cooler months. And although summer die offs occur in these shores (Williams 1993a;Kaehler and William 1996;Wai and Williams 2006) especially for sessile invertebrates and foliose macroalgae, the observed barrenness and patchy distribution of erect algae in the open and control treatments supports our hypothesis that grazers are the major causes of low recruitment of erect algal cover. This 'topdown effect' have been observed in many rocky shores such as in earlier studies (Connell 1961;Paine 1966;Castenholz 1961;Menge 1977) while bottom up regulation developed mainly from plant ecologists (Fretwell 1977(Fretwell , 1987Grime 1977;Oksanen et al 1981) who sees plants as the main provider of food and nutrient sources for organisms thereby controlling the food chain; this study however did not find any bottom up effect probably as this was conducted on protected shores.…”

Section: Top-down Control and Shifts In Assemblagesupporting

confidence: 63%

“…Throughout the cool season, foliose macroalgae can be found growing in most rock pools (see Wai and Williams 2006) but evidently this happens only as a result of escape from herbivores because to a wide extent the mid-shore of a semi-exposed site are quite barren from foliose algae except from cryptic habitats such as cracks, crevices and pools. Even in rock pools the most common algae are the crustose coralline forms and green erect foliose cover in the shores.…”

Section: B45mentioning

confidence: 99%

“…The Hong Kong rocky shores have been much studied on grazer-alga interaction such as on the effects of seasonality (Williams 1993(Williams , 1994, recruitment of erect and encusting algae (Kaehler and Williams 1997), grazer pressure (Harper and Williams 2001;Hutchinson and Williams 2003a;Wai and Williams 2006), typhoon (Hutchinson and Williams 2003b), cyanobacteria (Nagarkar and Williams 1997), and succession (Williams et al 2000). However the system was much studied, scale up of these previous studies remains rare and effects of processes at work at the scale of tens of meters to hundreds of meters may not work in the scale of thousands of meters; the findings remain limited to the areas of study.…”

Section: Bintroductionmentioning

confidence: 99%

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Variability and community organization in moderately exposed tropical rocky shore algal communities as influenced by different consumer groups

Macusi

2008

Nature Precedings

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Section: Top-down Control and Shifts In Assemblagesupporting

confidence: 63%

Section: B45mentioning

confidence: 99%

Section: Bintroductionmentioning

confidence: 99%

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Variability and community organization in moderately exposed tropical rocky shore algal communities as influenced by different consumer groups

Macusi

2008

Nature Precedings

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“…Previous studies have shown Nerita species exhibit larger temporal variability in grazing activities compared with other grazers (Forrest et al 2001, Wai & Williams 2006. N. yoldii exhibited clear seasonal variability in behaviour, foraging for ~5 h d −1 in summer, which is similar to N. polita and N. textilis (Chelazzi 1982), but only ~2 h d −1 in winter.…”

Section: Environmental Variables and Temporal Variationmentioning

confidence: 80%

Small-scale temporal and spatial variability in foraging behaviour of the mid-shore gastropod Nerita yoldii on seasonal, tropical, rocky shores

Yeung¹,

Williams

2012

Aquat. Biol.

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Describing temporal variation in the foraging behaviour of intertidal gastropods is important to gain an understanding of the environmental conditions that constrain their activity patterns. Foraging behaviour in the tropical gastropod Nerita yoldi was mainly determined by the tidal cycle: individuals foraged when they were awash, or emersed when the rock was wet, migrating downshore to forage and upshore when they returned to refuges. Apart from tidal influences, foraging in N. yoldii also varied with season and tidal state. Individuals were generally more active in summer than in winter and on neap than spring tides; although small-scale daily variation existed. Such temporal variation may be caused by several interacting environmental variables, especially air temperature, pressure and irradiance, which influence physical conditions as well as individuals' metabolism. Individual foraging patterns were also highly labile between seasons: most individuals would stop and remain stationary on the open rock surface in winter, but returned to refuges after foraging in summer, a pattern probably driven by physical stress. The foraging behaviour of N. yoldii, therefore, is predictable on a coarse scale, in terms of when they are active, but highly labile in duration and foraging range, which indicates the importance of local, daily variation in environmental factors controlling foraging on shores that have strong temporal changes in abiotic conditions. KEY WORDS: Nerita · Foraging behaviour · Tropical shoreResale or republication not permitted without written consent of the publisher Aquat Biol 16: 177-188, 2012 Such lability in foraging behaviour represents important adaptive traits in organisms (Mery & Burns 2010). Climatic seasonality, for example, is a large time-scale temporal pattern that affects foraging behaviour owing to changes in physical stress, predation pressure and food availability as well as associated changes in tidal and diurnal conditions. As a result, such variation in foraging behaviour can make it difficult to define precise behavioural patterns of a species (Chapman & Underwood 1992a, Ng & Williams 2006, Santini et al. 2011.The gastropod genus Nerita Linnaeus 1758 (Neritacea) has a high abundance and diversity in tropical regions (Vermeij 1973). Most species, such as N. textilis (Chelazzi et al. 1983) and N. polita (Chelazzi 1982) are zonal shuttlers (Chelazzi et al. 1988), which forage from a refuge either up-or downshore during each tidal cycle before returning to their resting level (Chelazzi et al. 1988). Previous observations on the behaviour of Nerita have not, however, investigated longer-term variations in foraging patterns, such as monthly or seasonal variation, al though a longerterm study of N. plicata, N. textilis and N. undata in Kenya showed these species to be more active on spring than neap tides (Ruwa & Jaccarini 1988).Nerita are important herbivores in the Hong Kong rocky intertidal zone (Hill 1980). In contrast to other tropical localities where the foraging beh...

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“…This preemption of space by grazers has been reported in many temperate rocky shores such as in New South Wales (Underwood 1980;Underwood and Jernakoff 1981;Underwood et al 1983), in New England (Lubchenco and Menge 1978), as well as in Oregon coasts (Freidenburg et al 2007). This preemption of space occurs when grazers like limpets and coiled gastropods feed on microalgae by scraping the rocky substratum with their radulae (Steneck and Watling 1982;Hawkins et al 1989;Williams 1994;Wai and Williams 2006). Nicotri (1977) demonstrated that grazers can affect the abundance and density of microflora by reducing the amount of chl a content on rock surface investigated.…”

Section: Grazing and Microalgal Abundancementioning

confidence: 99%

Variability and community organization in moderately exposed tropical rocky shore algal communities as influenced by different consumer groups

Macusi

2008

Nat Prec

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Tropical rocky shores have been described as diverse and having a complex variety of consumers. This wide array of consumers has been studied to shed light on the different roles of consumers, particularly grazers on rocky shores and how they affect the relative abundance and distribution of sessile algal prey. One of the aims of ecology is to clarify factors that regulate and structure the abundance, growth and relationship of predators and preys in each habitat. Grazing is known as one of the most important determinants of growth and distribution of rocky shore communities. In this study a comparison between the different effects of fishes, crabs and molluscan herbivores on the relative abundances of microalgae and macroalgae from micro (hundreds of microns) to medium (tens of meters to kilometers) scales of spatial variability was conducted. At the start of the experiment several hypotheses were forwarded: 1) that herbivores will reduce the density of microalgae and macroalgal cover causing a barren appearance and ultimately reducing algal diversity where grazing intensity is highest across treatments, sites and shores; 2) and where grazing pressure is low, algal cover and diversity will be high; 3) and that fishes and crabs contribute significantly to maintaining a high grazing pressure in the area and that fishes control the algal assemblage in benign environments. These were evaluated by exclusion experiments and quadrat counts to determine the effects of grazers on different functional groups of algae. Microalgal density was assessed indirectly by measuring chlorophyll a from rock chips taken from the treatment plots. Microspatial variability of different sites was assessed by scoring digital micrographs of rock chips also taken from treatment plots. Algal cover of treatment plots was assessed by using digital photos taken during forthnightly visits in all sites. The univariate and multivariate results show significant differences across treatments, sites and shores and even significant temporal differences. Microalgal abundance and erect algal cover in fenced plots were significantly different compared to the other treatments. Grazer removal effectively caused a completely different algal assemblage to develop through time in cage and fenced treatments while maintaining a mostly barren cover in most open and control set-ups. Species which are not typically present in shores have grown inside cage and fenced treatments during the period of manipulation. Molluscan herbivores are the most effective grazers in these shores and control the relative distribution of algae by restricting the recruitment success of algal sporelings particularly erect macroalgae. Herbivorous fishes and crabs do not directly influence algal sporelings since the early stages of algae are too small for them to handle. But both consumers complement the removal of turf forming algae. The observed over all grazing effects show that molluscs have greater impact than fishes and crabs combined; the effect of either fishes or crabs are equal. Hence, the impact of crabs and fishes on these shores are minimal, mainly affecting turf forming algae. Moreover, the observed spatial variability in algal assemblage from micro to medium scales is mainly driven by high grazing intensity. Thus, grazing acts as a highly effective top down control mechanism in these shores during the cool winter season.

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Monitoring spatio-temporal variation in molluscan grazing pressure in seasonal, tropical rock pools

Cited by 14 publications

References 27 publications

Variability and community organization in moderately exposed tropical rocky shore algal communities as influenced by different consumer groups

Variability and community organization in moderately exposed tropical rocky shore algal communities as influenced by different consumer groups

Small-scale temporal and spatial variability in foraging behaviour of the mid-shore gastropod Nerita yoldii on seasonal, tropical, rocky shores

Variability and community organization in moderately exposed tropical rocky shore algal communities as influenced by different consumer groups

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