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vol.30 número1  suppl.SympInterannual Variability of the Meiobenthos and Hyperbenthos Communities from two Ecuadorian Sandy Beaches (1999-2001)Study of the Mussel Aulacomya ater, Molina, 1782 (Bivalvia: Mytilidae), near Santa Rosa Island, Independence Bay, Peru, during the El Niño Phenomenon 1997- 98 índice de autoresíndice de materiabúsqueda de artículos
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Investigaciones marinas

versión On-line ISSN 0717-7178

Investig. mar. v.30 n.1 supl.Symp Valparaíso ago. 2002

http://dx.doi.org/10.4067/S0717-71782002030100044 

Variation of the Intertidal
Macrozoobenthos Community of a
Sandy Beach during El Niño/Southern
Oscillation, Lambayeque, Peru.

J. Fupuy1, V. Alvitres1, J. Chanamé2

1Universidad Católica Santo Toribio de Mogrovejo,
Peru, E-mail: jafupuy@hotmail.com
2Universidad Nacional Pedro Ruiz Gallo, Peru,
E-mail: jchaname@hotmail.com

Objectives

Peru is one key country affected by "El Niño", which is known to have repercussions throughout the world. This forces the Peruvian Government to lead to improve our understanding of the mechanisms that generate "El Niño", and further, to enable its prediction, so as to diminish the negative impacts and exploit the benefits that it can bring. Knowledge of the "El Niño" events depends on the quality and quantity of available information, because it allows us, by means of analysis, to predict the future tendency and the impact of "El Niño" and "La Niña" events. The purpose of this research was to study the variability of the intertidal macrozoobenthos community of a sandy beach (Lambayeque, Perú) during "El Niño" after the El Niño 1997/98.

Results & Discussion

The presence of 17 species of organisms of the intertidal macrozoobenthos of sandy beaches in San José Lambayeque, Perú differs according to "El Niño" phases (Table 1).

Table 1 Species composition of the intertidal Macrozoobenthos community of the sandy
San José beach, Lambayeque, Perú, before, during and after the "El Niño" event 1997-98.

BEFORE

DURING

AFTER

Donax sp.

Donax sp.

Donax sp.

Olivella columellaris.

Olivella columellaris.

Olivella columellaris.

Lumbrineris sp.

Lumbrineris sp.

Lumbrineris sp

Nephtys sp.

Nephtys sp.

Nephtys sp.

Glyceridae (Fam.)

Glyceridae (Fam.)

Glyceridae (Fam.)

Exirolana braziliensis

Exirolana braziliensis

Exirolana braziliensis

Emerita analoga

Emerita analoga

Emerita analoga

Lepidopa chilensis

Lepidopa chilensis

Lepidopa chilensis

Callianassa islagrande

Callianassa islagrande

Callianassa islagrande

Pagurus sp.

Ocypode gaudichaudii

Pagurus sp.

Ocypode gaudichaudii

Callinectes sp.

Ocypode gaudichaudii

Sergestidae sp.

 

Callinectes sp.

Pinixa sp.

 

Nereis sp.

   

Scolelepis sp.

   

Nemertino

Water temperatures (TSM) were plotted through time (months) along with the occurrence of the El Niño (Fig. 1). It was observed that diversity has the same tendency as temperature in the normal phase of "El Niño", but in the cold phase ("La Niña") a phase displacement of 1 to 2 months occurred. Furthermore, it should be noted that diversity is inverse to temperature in the second phase of "El Niño" and during April-Sep 1996 (normal phase?), which indicates a homogeneity of the populations in this community, that is to say that there is no prevalence of a single species. The high TSM generated during "El Niño" 1997-98 generated a fall in diversity and an increment of this index in the `normal phase`. The most important species reported were: Donax sp., O. collummellaris, E.analoga, Lumbrineris sp and Nephtys sp.


Fig. 1 Fluctuation of the Shannon - Wiener index through time with TSM (a) and enlarged view of the "El Niño" phase of 1997-98(b).

In the case of Donax sp and O. collummellaris, both species behave similarly in response to "El Niño", expressed months later, one reason that density and biomass increased during the second phase of "La Niña".

Emerita analoga (Crustacea), is one of the most important populations because of its location in the trophic chain and sensitivity to the onset of "El Niño": as much in terms of population as in biological aspects, which are the topic of another work (see: Effects of event "La Niña" 98-2000 on the population structure of Emerita analoga, Lambayeque - Perú, by Víctor Alvitres, Jorge Fupuy, Jorge Chanamé, Adela Chambergo, Miguel Cortez). Density and biomass for this population increased when the temperature increased ("El Niño" 1997-98, phase 1) up to a certain range, then becoming harmful (Fig. 2). Presently the population is recovering within the intertidal community.


Fig. 2 Variation of the density (ind/m2) in the different phases of the "El Niño" cycle of Lumbrineris sp. Nephtys sp., Emerita analoga and Olivella collummellaris

The polychaeta is another group of ecological importance and, for their behaviour as a population, essential for the diagnosis of "El Niño". Lumbrineris sp. is a species favored by "El Niño", because it increases its biomass and density favouring its prevalence inside the community; on the other hand Nephtys sp. is a species which is negatively affected, although it proliferates in cold periods in the sandy intertidal zone.

In the analysis of the relationship between temperature and density, it was observed that Emerita analoga and Nepthys sp. presented a high correlation coefficient (r = -0,64 a -0,78), increasing in normal periods and cold periods and diminishing in warm periods. In the temperature - biomass relationship, Lumbrineris sp had the better correlation coefficient (r = 0,77).

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