Transcript Scientific Investigation Process

Hi, my name is Jason Morton, I’m a marine scientist from Avondale University

College and I've been studying rocky shores like this one at Bateau Bay on the Central Coast of New South Wales for over 20 years.

Scientists work within a framework called the scientific method. This starts with

making observations and inquiring. This then leads to the second step of the scientific method which is the development of a question to be answered and a hypothesis, which is a tentative answer to that question for example after protecting a rocky shore from harvesting snails urchins etc the question could be asked

is protection of the rocky shore resulting in an increase in the number of species present a tentative answer to this question would be, yes there are more species on protected rocky shores compared to those that are not protected

The third step of the scientific method is to obtain data and analyze it. In this

presentation we'll be looking at different ways that data is obtained on the rocky shore.

To investigate a rocky shore we obviously can't count everything and so a subset or a sample is done of the entire area. These samples should be representative of the area to be studied.

The main ways to do this are to use time searches quadrats or transects.

These can be used to record everything you find or they can focus on only a few or even just one species.

The simplest method of sampling on a rocky shore is to use a timed search within a

Defined area. These are usually done to generate a species list for a site

or to record abundances of species that are so rare that large areas are needed to be sampled.

Timed searches need to be systematic and also have to be done in a defined time say 30 minutes. Quadrats are framed squares that are relatively small such as this one here which is a half by half metre.

Quadrats are placed on the rocky shore typically on flat surfaces and the abundances of each species is counted. For highly abundant species such as

Connie Winks estimates of abundances may be needed. This is done by counting individuals in only a portion of the quadrat and then extrapolating to estimate the number in the entire quadrat. For species such as seaweeds it may be best to record the percentage coverover the rock within the quadrat quadrats can be positioned in one of four main ways on the rocky shore.

The easiest and quickest method for sampling is to haphazardly place quadrats on the rocky shore however haphazard placement of quadrats can introduce a lot of researcher bias as some areas can be chosen to be selected whilst others are avoided. One way to avoid researcher bias is to be truly random in the placement of quadrats.

The rocky shore must first be divided into a grid and random numbers are used to select where the quadrats should be placed.

There is no bias but it is possible that important areas on the rocky shore are missed including entire zones.

A simpler and often better approach is to evenly space quadrats around the rocky shore. This is termed systematic placement. This removes bias and also ensures most of the rocky shore is represented.

Stratified placement of quadrats recognises that rocky shores contain distinct zones or strata and that each needs to be sampled. Often some zones will only need a few quadrats to represent the creatures in that zone whilst others need many quadrats.

Within each strata either the haphazard random or systematic approaches can be used to determine where to place the quadrats. Line transects are similar to quadrats but rather than being square they are long and can stretch from the low to the high intertidal zones to ensure all zones are captured or can be used to sample individual crevices line.

Transects are used one of two main ways, the first is to count the abundances of each species within a defined width beside the transect. A second way for seaweeds, is the presence or absence of species is noted at a certain number of points along the transect. There could be as many as a hundred of these points.

So how do you know how much of the rocky shore you need to sample to obtain good data? Well, obviously a two minute time search isn't long enough and who has the time for six hours? Similarly two quadrats are not enough and hundreds would take too long, we must therefore optimize our time whilst also obtaining valuable data. A simple way of doing this is, if extra time or more quadrats does not add any new species then this is a good point to stop.

One way to represent this is to construct a species area curve. Species area curves increase rapidly at the start as new species are captured but as they start to flatten out, this is the point where quadrat sampling is usually stopped.

In the Supra Littoral zone it may be that only three or four quadrats are needed but in the Lower Littoral maybe more than 10 are needed.

So you now know some methods for sampling rocky shores to obtain data

the next step is to look at your data and then move to the final step of the scientific method that is re-look at your question, come to a conclusion and then come up with some more questions.