Distribution of Meiofaunal biodiversity and abundance in relation to development stage of the Mangrove Forest

Abstract

Mangrove ecosystems constitute a valuable economic resource harbouring a wide diversity of organisms and operating an essential provider of nutrients for adjoining marine ecosystems. The meiobenthic fauna (i.e. small benthic invertebrates) plays an important role in the food chain and has proven to be a useful indicator on environmental stressors within the mangrove forest. This study is conducted to investigate the relationship between meiobenthic fauna and mangrove development stage. The distribution, density and biodiversity were measured in the Longhai Mangrove Nature Reserve, southwest of Xiamen, China. Three replicate samples were collected from three planted mangrove forests at different age stages. Additionally, a control site was chosen, constituted by a mudflat with no observed vegetation. Significant patterns were recognized regarding biodiversity, which increased from the lower age to the higher, at a level of p = 0.004 (R2 = 0.616). Nematodes constituted the most abundant group >90 %, followed by oligogchaetes 1.5-5.6 %. The control site appeared to have the lowest number of groups observed (total 3) and was found in significantly lower level of biodiversity compared to the highest age of the mangrove sites. Considering older mangrove forests indicate higher biodiversity this may indicate the importance of preserving the presence of aging mangrove ecosystems.

Popular Abstract

The Advantage of Ageing : Mangrove Forests

The mangrove ecosystems complex structure is made up of unrelated taxa of woody trees and shrubs, that have all adapted to extreme environmental conditions of high salinity, wind, water and tides. Mangroves are mainly located in tropic climates and can be found on both sides of the equator in saline regions along embayment and estuaries. It generally harbours a few plant species but can nevertheless contain an immense biomass.

Mangrove plants are considered ecosystem engineers, which means they directly affect their surrounding environment in a way that becomes facilitating for other organisms. The complex root system provides a substrate for sessile marine organisms while also acting shelter for several marine species and their juveniles that may find protection from predators. Furthermore, mangroves function as flood control barrier and a protector of coastal landmass from tides, high winds etc. It also hinders coastal erosion and showed to have a marked protection against the tsunami of 2004 compared to non-mangrove coastlines. Mangroves even contribute significantly to the global carbon cycle by producing organic carbon well in excess of the ecosystem requirements.

Due to several anthropogenic factors, the mangrove forest is threatened and approximately one-third of the world’s mangrove forests have been lost during the last half-century. Main causes of mangrove destruction are establishment of aquaculture shrimp farms, urban development, overexploitations of timber, fish, shellfish etc. However, in the early 1990s, the Chinese government began to invest in mangrove reforestation to regain the ecosystem services that the mangrove forest provides.

To be able to understand the gain of planting mangroves, an investigation was made on the establishment of meiobenthic faunal communities over time by studying planted mangroves of different ages. Small sediment-living organisms (<500 μm) called meiobenthic fauna serve an important role in the benthic food chain, both as food resource for larger benthic organisms
(macrobenthos), such as crabs and fish, as well as decomposers of detritus material. By conducting such survey, one may increase the knowledge on whether planted mangroves can contribute to increased biodiversity, and provide information that may gain further studies in examining mangrove forests.

Three sites were chosen, representing ages of 17, 30 and 53 years old. Additionally a control site constituted by a mudflat (no observed vegetation) was chosen in the same area as mangrove sites to compare biodiversity levels to non-mangrove. At each site three sample cores (Ф=2.9 cm) were randomly distributed. By counting and dividing meiobenthic groups into major taxa, calculate a biodiversity index and compare between different ages, one could determine a significant increase in biodiversity over time.

Comparison between control site and mangrove sites showed significantly higher biodiversity for the oldest mangrove (53 years). While none of the other sites were significant to control, one also noticed that the oldest site had significantly higher biodiversity compared to the youngest. However, the most important result was the significant increase in biodiversity from age 17 to age 53, which indicates the importance of preserving aging mangrove ecosystems

Supervisors: Bengt Hansson, Lund University; Hongyou Hu, Xiamen University
Degree Project in Biology, 15 credits, 2017
Department of Biology, Lund University
(SIDA: Minor Field Studies)

• author: Hultman, Matilda
• supervisor: Bengt Hansson
• organization: Degree Projects in Biology
• course: BIOK01 20171
• year: 2017
• type: M2 - Bachelor Degree
• subject: Biology and Life Sciences
• language: English
• id: 8925705
• date added to LUP: 2017-09-15 11:52:30
• date last changed: 2017-09-15 11:52:30