1. Prof. Dr. Hanan Mitwally, Marine Biology
Meiofauna
Prof. Dr. Hanan Mitwally, Marine Biology

2. Prof. Dr. Hanan Mitwally, Marine Biology
Expectations
?? ?
Prof. Dr. Hanan Mitwally, Marine Biology

3. Prof. Dr. Hanan Mitwally, Marine Biology
Objectives
Definition
Abiotic conditions affecting meiofauna.
What taxa are meiofauna?
Adaptations of meiofauna.
Meiofauna community zonation.
Meiofauna life history and diversity traits.
More variation in meiofauna communities.
Meiofauna food webs.
Prof. Dr. Hanan Mitwally, Marine Biology

4. Prof. Dr. Hanan Mitwally, Marine Biology
Definition
The tiny, but abundant, organisms that live in sand and mud.
They are > .062 mm, but < 0.5mm
Endobenthic organisms plow through interstitial space by displacing particles.
Mesobenthic live within the interstitial spaces.
Epibenthic organisms live at the sediment water interface.
Prof. Dr. Hanan Mitwally, Marine Biology

5. Prof. Dr. Hanan Mitwally, Marine Biology

6. Prof. Dr. Hanan Mitwally, Marine Biology
Benthic organisms can live on the ocean floor (epifauna/epiflora) or in the ocean floor (infauna).
Which type (epi/in) depends on the particle size?.
Why are the few large organisms associated with
cobble and shingle? Activity 1
Why is there no “inflora”?
Highest
meiofauna
numbers
Prof. Dr. Hanan Mitwally, Marine Biology

7. Prof. Dr. Hanan Mitwally, Marine Biology
Abiotic conditions affecting meiofauna
The following abiotic factors affecting meiofauna
Rearrange them according to their importance to meiofauna.
Temperature,
wave action,
Water circulation,
Grain size, Activity 2
Salinity,
Oxygen
Prof. Dr. Hanan Mitwally, Marine Biology

8. Prof. Dr. Hanan Mitwally, Marine Biology
Abiotic conditions affecting meiofauna
Environmental conditions affecting the meiofauna are somewhat different from those that affect the macro fauna in the same area.
The most important factor influencing meiofauna is grain size (why?)
Because this has a strong influence on other abiotic conditions.
Prof. Dr. Hanan Mitwally, Marine Biology

9. Prof. Dr. Hanan Mitwally, Marine Biology
Coarse grain size Vs fine grain size
Coarse grain size means greater interstitial space.
Fine grain size means less interstitial space.
Coarse-grained sediments hold less water by
capillary action than fine-grained sediments.
Prof. Dr. Hanan Mitwally, Marine Biology

10. Prof. Dr. Hanan Mitwally, Marine Biology
Salinity and waves
Reductions in salinity due to flooding with
fresh water usually affect only the uppermost
layers of sediment (Why?)
Because the lower layers retain seawater by capillary action.
Wave action churns up the sediment, constantly rearranging it and increasing the chances of throwing the meiofauna into the open water.
Prof. Dr. Hanan Mitwally, Marine Biology

11. Prof. Dr. Hanan Mitwally, Marine Biology
Abiotic conditions affecting meiofauna
Circulation of water and oxygen is greater in coarse
sediments and reduced in fine-grained sediments.
In very fine grained sediments, such as mud, water
circulation practically ceases, the interstitial habitat
becomes anoxic, and the meiofauna disappears.
Temperature is another factor of importance in determining presence, absence, and distribution of meiofaunal organisms.
Temperatures are most variable in the surface layer of
sediment, and the variability decreases with depth.
Prof. Dr. Hanan Mitwally, Marine Biology

12. Prof. Dr. Hanan Mitwally, Marine Biology
What taxa are meiofauna?
The types of organisms constituting the meiofauna include a broad range of invertebrate phyla dominated by those phyla that normally have small enough sizes to fit between the sediment grains.
Phyla that consist primarily of large or sedentary or sessile organisms are poorly represented in the meiofauna.
Prof. Dr. Hanan Mitwally, Marine Biology

13. Prof. Dr. Hanan Mitwally, Marine Biology
Phyla or Group
1- Gastrotricha
2- Crustacea/Ostracoda
3-Crustacea/Copepoda/Harpacticoidea
4- Nematoda
5- Turbellaria
6-Nemertina
7-Archiannelida
8-Polychaeta
9-Oligochaeta
Prof. Dr. Hanan Mitwally, Marine Biology

14. Prof. Dr. Hanan Mitwally, Marine Biology
POLYCHAETE
NEMATODE
TARDIGRADE
GASTROTRICH:
CRUSTACEA: HARPACTICOID COPEPOD
CRUSTACEA: OSTRACOD
Prof. Dr. Hanan Mitwally, Marine Biology

15. Prof. Dr. Hanan Mitwally, Marine Biology
Adaptations of meiofauna
The most obvious adaptation of meiofaunal organisms is that they are :
1-Very small in size.
2- Elongated or vermiform in shape and flattened.
3-An adaptation to the dynamics of sediment movement is the presence of skeletons that offer some protection against crushing.
4-Most animals in the interstitial are free-moving and have various adaptations to cling to the sediment grains.
5- Statocysts, organs that detect gravity.
Prof. Dr. Hanan Mitwally, Marine Biology

16. Prof. Dr. Hanan Mitwally, Marine Biology
Meiofauna community zonation
The composition of the meiofauna varies both horizontally and vertically in the substrate, and most are concentrated in the upper layers.
Vertical zonation of meiofauna in the sediment appears to be related to oxygen concentration and/or predation.
Vertical migration triggered by temperature or salinity changes is especially prominent in temperate zone beaches.
Prof. Dr. Hanan Mitwally, Marine Biology

17. Prof. Dr. Hanan Mitwally, Marine Biology
Meiofauna life history Temporary meiofauna consists of newly settled juveniles of macrofaunal organisms,
Permanent meiofauna consists of organisms that spend their entire lives in the interstices of the sediment.
Due to their small size, meiofauna produce very few eggs and ensure their fertilization and survival by various mechanisms that retain the embryos in the interstitial space.
Sperm transfer is direct, including spermatophore.
Prof. Dr. Hanan Mitwally, Marine Biology

18. Prof. Dr. Hanan Mitwally, Marine Biology
Meiofauna diversity traits
Worldwide, the average number of meiofaunal organisms per square meter is 106.
Diversity was measured as 70 spp. per 50 cm2 of sand.
There is no apparent gradient in richness with change in latitude.
Prof. Dr. Hanan Mitwally, Marine Biology

19. Prof. Dr. Hanan Mitwally, Marine Biology
More Variation in Meiofauna Communities
There are also seasonal changes in abundances of organisms and species composition.
Factors affecting seasonal abundances of meiofauna
1- Primary productivity Predation.
Meiofauna are sensitive to natural or human-induced
perturbations.
Meiofauna are distributed patchily, even where the sediment grain size is homogeneous.
There is little information on the long-term variability of meiofaunal communities, and the information that is available is conflicting.
Prof. Dr. Hanan Mitwally, Marine Biology

20. Prof. Dr. Hanan Mitwally, Marine Biology
Meiofauna food webs
Trophic relations among the components of the interstitial
fauna are not well known.
Predators on the meiofauna include certain fishes and
macrofaunal deposit feeders that kill meiofauna when they ingest the sediment. There are also meiofaunal predators.
The meiofauna also contains herbivores, detritus feeders,
and suspension feeders,
The significance of meiofauna to macrofaunal communities
and food webs appears to depend on the sediment type.
Meiofauna is more significant to macrofauna in finer
sediments, probably partly due to the concentration of the
meiofauna in the top layers, where they are more accessible.
Prof. Dr. Hanan Mitwally, Marine Biology

21. Success Is An Energy Inside us God Supports It.
Summary
Take Home Message
Success Is An Energy Inside us God Supports It.
Prof. Dr. Hanan Mitwally, Marine Biology