Elevation and sediment dynamics: A diversity of tactics

A long-term research project I’ve been involved with has just been published by Estuarine, Coastal and Shelf Science. The paper is available for free at this link until March 13th 2016. The paper describes our understanding of the trajectories of two salt marshes that are following disparate paths; one that’s deteriorating and one that’s stable (Fig. 1).

Figure 1. Sherwood (A) and Jarvis creek (B) marshes. See our manuscript for a detailed explanation (link in text above).

The paper draws on nearly a decade’s worth of data, and among other things, it compares six ways of measuring sedimentation. It’s abnormal to have so many different methods used in the same system, but I think we show that there’s a lot to be gained from doing so.

It may seem unnecessarily duplicative to measure sediment dynamics in so many ways, but the idea is that each method actually measures slightly different things, and when taken together they contribute to a fuller picture of the ecosystem. Each method operates on characteristic scales in time and space, and documents different processes. Figure 2 shows relationships between the temporal and spatial scales covered by some methods for examining marsh sediment dynamics.

 

Figure 2. Temporal and spatial scales for selected measures of sediment dynamics

 

Disagreement between the methods shown in Figure 2 may actually be quite informative about the nature of sediment regimes in an ecosystem. Considering the spatial and temporal scales relevant to each method, we might gain insights into whether sediment dynamics are dominated by, for example, infrequent pulses of sediment versus smaller but perhaps more regular deposition.

It can be frustrating to be faced with an abundance of methods for measuring some process (primary productivity is a perfect non-sediment example). When a study uses a single method, it can be difficult to know when differences between studies reflect real processes or artifacts of the different methods used. I think that in many cases, an abundance of methods is something that should be nurtured, since they provide a better understanding of the world around us than would any single method deployed universally.