Friends or Foes? Sponges and ascidians overgrowing corals: The new challenge for reef fishes

Latest update July 29, 2019 Started on November 1, 2018
sea

Coral reefs are shifting toward environments dominated by sponges and ascidians in Papua New Guinea. We will witness how one of the most diverse fish communities in the world could adapt in a sponge and ascidians dominated environment.

November 1, 2018
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Preparation

Cracking the riddle: sponge identification


Soon we will start identifying the sponges from Papua New Guinea. To accurately describe these organisms it is crucial to keep track of their shape, colour and texture when the specimens are alive; and to obtain some samples of their tissue. Tissue samples can be used to observe spicules which are hard and sharp needle shape structures that protect and provide support to the body of the sponges. The description of these parts will help us to start cracking the riddle.

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How many species are there???....


Such an interesting and difficult question! Sponges and ascidians have been usually overlooked because they are complicated to identify at species level. They have diverse morphologies and complex interactions, for instance, they can have photosynthetic organisms in their tissues that help them to get food! Currently, it is estimated that there are 8,553 sponge and 2,300 ascidian species in the world. However, these numbers are changing rapidly as can be checked in the World Porifera Database (http://www.marinespecies.org/porifera/). There are no previous records of sponges and ascidians in Kimbe Bay, and our expedition is pioneering these numbers. We have explored up to 15 meters depth, because of logistic constrains during SCUBA diving. However, additional methodologies like the use of Remote Operated Vehicles (ROV) could aid to go beyond that depth and unravel a larger diversity of sponges. In the future we will be working on how to identify sponges thanks to the aid of a sponge expert who will join the research team! Keep an eye on this expedition and I hope to give you the number of species and potentially new species for the world in the near future.

¿Cuantas esponjas hay allí? ¡Es una pregunta muy interesante y muy difícil de responder! Las esponjas y ascidias normalmente son ignoradas porque es complicado identificarlas a nivel de especie. Ellas tiene formas diversas e interacciones complejas, por ejemplo, pueden tener organismos fotosintéticos en sus tejidos que les ayudan a obtener alimento. Actualmente se estima que hay 8,553 esponjas y 2,300 ascidias en el mundo. Pero estos números están cambiando rápido como puede verse en la Base de datos Mundial de Porifera (http://www.marinespecies.org/porifera/). No hay un registro previo de esponjas o ascidias en la Bahía de Kimbe, y nuestra expedición será pionera en obtener esos números. Hemos explorado hasta los 15 metros de profundidad por limitaciones logísticas con buceo SCUBA. Sin embargo, otras medotologías como el uso de Vehículos de Operación Remota podrían ayudarnos a sobrepasar esa barrera y descubrir una diversidad de especies mucho mayor. En el futuro aprenderemos como identificar esponjas con la ayuda de un experto en esponjas que se unirá a nuestro equipo de investigación. Manténgase atentos en nuestra expedición y espero poder darles el dato sobre el número de especies y probablemente nuevas especies para el mundo en un futuro próximo.

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Really interesting, have fun doing your research en PNG
Expedition Background

Numerous anthropogenic disturbances are contributing to coral reef degradation around the world and threatening the biodiversity of reef-associated species. As a consequence, other sessile organisms including sponges, ascidians and algae could replace corals as the major habitat-forming organisms. However, these organisms are unlikely to perform the same ecological functions that corals provide and could exert detrimental impacts on organisms that are strongly associated with complex coral habitat. In my expedition I will attempt to investigate how sponges and ascidians affect corals species via competition for benthic habitat. Additionally I will test the impacts that shifting to a sponge or ascidian dominated environment might have on coral reef fish assemblages. This expedition will be conducted at Kimbe Bay, Papua New Guinea, which is an area located in the centre of the biodiversity hotspot for corals and fishes. Thus, this natural laboratory provides a unique opportunity to observe how one of the most diverse fish communities in the world could be affected by a sponge or ascidians dominated environment and generate the first insights into the ecological changes that coral reef fishes will be confronting in these emergent habitats in the near future.

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Thanks for all your questions!
I will address them in future post, so keep an eye on this expedition.
Would you do some comparison on fish community and their habitat preference, between corals, sponges and ascidians?

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