Composição e variação temporal e nictemeral da fauna zooplanctônica na zona de arrebentação em Praia Grande, SP
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Data
2017-01-16
Autores
Moreno, Danubia [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
As áreas costeiras de baixa profundidade, como zonas de arrebentação de praias arenosas são pouco estudadas quando comparadas a outros ecossistemas costeiros. No entanto, são consideradas de grande importância ecológica, pois abrigam alta diversidade de organismos que se alimentam, reproduzem e buscam na região proteção contra predadores. A falta de estudos deve-se principalmente à alta hidrodinâmica existente, sendo muitas vezes difícil de amostrar, principalmente no período noturno. Este estudo analisou a variação temporal e nictemeral da fauna zooplanctônica existente na zona de arrebentação da Praia da Aviação que trata-se de uma praia densamente habitada localizada no município de Praia Grande na costa central do estado de São Paulo. Os organismos foram coletados com rede de plâncton através de arrastos horizontal, superficial e perpendicular à praia em profundidade de 1m. Dados de temperatura e salinidade também foram obtidos juntamente com observações visuais do estado de agitação do mar, vento local e nebulosidade. Este processo ocorreu bimensalmente entre Junho de 2013 e Abril de 2015 durante os períodos diurno e noturno, visando avaliar a variação na composição zooplanctônica e sua relação com as migrações verticais. O zooplâncton da praia analisada foi representado por 116 táxons, englobando organismos holoplanctônicos, meroplanctônicos, bentônicos (presentes na coluna d’água devido à alta turbulência) e bentoplanctônicos (organismos que realizam migração vertical). A composição da fauna foi bastante diversificada e, ao longo de todo o estudo, foi constatada pouca variação na diversidade entre os períodos de amostragem além de discreta variação sazonal. A abundância total de organismos planctônicos capturados no período diurno variou de 384 a 14.746 org.m-³ (4.153,1 ± 5.766 org.m-³) e, durante a noite de 504 a 67.269 org.m-³ (7.845,3 ± 18.844 org.m-³). A comunidade zooplanctônica demostrou uma diferença significativa (p <0.000), em termos de abundância, entre a fauna holoplanctônica, meroplanctônica e bentoplanctônica. A maior abundância e percentual de contribuição dentre os holoplanctônicos foi atribuída aos grupos Copepoda, Cladocera seguida de Tunicata, já os meroplanctônicos destacaram os grupos Mollusca e Echinodermata e, dentre os bentoplanctônicos o grupo Mysida. A fauna zooplanctônica apresentou, em matéria abundância, uma variação temporal com distinções significativas (p < 0.000) em cada mês de amostragem, sendo os valores registrados no verão similares entre si (85%), porém distintas das demais estações (<40%). Contudo, não foram detectadas diferenças significativas de abundância (p = 0.299) relacionada à variável ambiental temperatura da água. Durante o período noturno foi registrado maior quantidade de organismos existentes na coluna d’água, e o incremento da fauna ocorreu principalmente pela maior frequência de misidáceos, larvas de decápodos e peixes juvenis neste período, no entanto, a maior ocorrência desses organismos durante a noite não refletiu estatisticamente diferenças (p = 0.123) na abundância total da fauna em relação ao período diurno. De maneira geral, detectou-se neste estudo que a zona de arrebentação da Praia da Aviação dispõe de uma abundante e rica comunidade zooplanctônica que reflete, em termos de composição e abundância, o caráter dinâmico da região, onde processos ambientais e bióticos influenciam nas mudanças recorrentes da estrutura da comunidade zooplanctônica que é responsável pela manutenção da vida marinha costeira.
Low depth coastal areas, such as surf zones at the sand beaches, are poorly studied when compared to other coastal ecosystems. However, they are considered of great ecological importance, because they shelter a high diversity of organisms that feed, reproduce and seek protection in the region against predators. The lack of studies is mainly due to the existing high hydrodynamics, and is often difficult to sample, especially at night. This study analyzed the temporal and nictemeral variation of the zooplankton existing in the surf zone of Praia da Aviação, a densely populated beach, located in the Praia Grande city, on the central coast of the State of São Paulo. The organisms were collected with plankton net through horizontal trawls, superficial and perpendicular to the beach in depth of 1m. Temperature and salinity data were also obtained along with visual observations of the state of sea agitation, local wind and cloudiness. This process occurred bimonthly between June 2013 and April 2015 during the day and night periods, With the objective of evaluating the variation in zooplankton composition and its relationship with vertical migrations. The zooplankton of the beach was represented by 116 taxa, including holoplanktonic, meroplanktonic, benthic organisms (present in the water column due to the high turbulence) and bentoplanktonic organisms (organisms that perform vertical migration). The faunal composition was quite diverse and, throughout the study, there was little variation in the diversity between the sampling periods as well as discrete seasonal variation. The total abundance of planktonic organisms captured in the daytime ranged from 384 to 14,746 org.m-³ (4.153.1 ± 5.766 org.m-³) and, during the night from 504 to 67,269 org.m-³ (7,845.3 Ñ 18,844 org.m-³). The zooplankton community demonstrated a significant difference (p <0.000), in terms of abundance, between the holoplankton, meroplankton and bentoplankton fauna. The highest abundance and percentage of contribution among the holoplanktonic species were attributed to the Copepoda, Cladocera and Tunicata groups, whereas in the meroplankton fauna the groups Mollusca and Echinodermata were highlighted, and among the bentoplankton the Mysida group. The zooplankton fauna presented a temporal variation with significant distinctions (p<0.000) in each month of sampling, with similar summer values (85%), but distinct from the other seasons (<40%). However, there were no significant differences in abundance (p=0.299) related to the environmental variable water temperature. During the night period, more organisms were recorded in the water column, and the increase of the fauna occurred mainly due to the higher frequency of Mysida, decapod larvae and juvenile fish in this period, however, the higher occurrence of these organisms during the night did not statistically reflect differences (p = 0.123) in the total fauna abundance in relation to the daytime period. In general, it was detected in this study that the Praia da Aviação surf zone has an abundant and rich zooplankton community that reflects, in terms of composition and abundance, the dynamic character of the region, where environmental and biotic processes influence the Recurrent changes in the structure of the zooplankton community which is responsible for the maintenance of coastal marine life.
Low depth coastal areas, such as surf zones at the sand beaches, are poorly studied when compared to other coastal ecosystems. However, they are considered of great ecological importance, because they shelter a high diversity of organisms that feed, reproduce and seek protection in the region against predators. The lack of studies is mainly due to the existing high hydrodynamics, and is often difficult to sample, especially at night. This study analyzed the temporal and nictemeral variation of the zooplankton existing in the surf zone of Praia da Aviação, a densely populated beach, located in the Praia Grande city, on the central coast of the State of São Paulo. The organisms were collected with plankton net through horizontal trawls, superficial and perpendicular to the beach in depth of 1m. Temperature and salinity data were also obtained along with visual observations of the state of sea agitation, local wind and cloudiness. This process occurred bimonthly between June 2013 and April 2015 during the day and night periods, With the objective of evaluating the variation in zooplankton composition and its relationship with vertical migrations. The zooplankton of the beach was represented by 116 taxa, including holoplanktonic, meroplanktonic, benthic organisms (present in the water column due to the high turbulence) and bentoplanktonic organisms (organisms that perform vertical migration). The faunal composition was quite diverse and, throughout the study, there was little variation in the diversity between the sampling periods as well as discrete seasonal variation. The total abundance of planktonic organisms captured in the daytime ranged from 384 to 14,746 org.m-³ (4.153.1 ± 5.766 org.m-³) and, during the night from 504 to 67,269 org.m-³ (7,845.3 Ñ 18,844 org.m-³). The zooplankton community demonstrated a significant difference (p <0.000), in terms of abundance, between the holoplankton, meroplankton and bentoplankton fauna. The highest abundance and percentage of contribution among the holoplanktonic species were attributed to the Copepoda, Cladocera and Tunicata groups, whereas in the meroplankton fauna the groups Mollusca and Echinodermata were highlighted, and among the bentoplankton the Mysida group. The zooplankton fauna presented a temporal variation with significant distinctions (p<0.000) in each month of sampling, with similar summer values (85%), but distinct from the other seasons (<40%). However, there were no significant differences in abundance (p=0.299) related to the environmental variable water temperature. During the night period, more organisms were recorded in the water column, and the increase of the fauna occurred mainly due to the higher frequency of Mysida, decapod larvae and juvenile fish in this period, however, the higher occurrence of these organisms during the night did not statistically reflect differences (p = 0.123) in the total fauna abundance in relation to the daytime period. In general, it was detected in this study that the Praia da Aviação surf zone has an abundant and rich zooplankton community that reflects, in terms of composition and abundance, the dynamic character of the region, where environmental and biotic processes influence the Recurrent changes in the structure of the zooplankton community which is responsible for the maintenance of coastal marine life.
Descrição
Palavras-chave
Zona de arrebentação, Zooplâncton, Migração vertical, Variação nictemeral, Surf zone, Zooplankton, Vertical migration, Nictemeral variation, Zona de rompientes, Zooplancton, La migración vertical, Variación diurna